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      FFmpeg Codecs Documentation
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      <h1>
      FFmpeg Codecs Documentation
      </h1>
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<a name="SEC_Top"></a>

<a name="SEC_Contents"></a>
<h2 class="contents-heading">Table of Contents</h2>

<div class="contents">

<ul class="no-bullet">
  <li><a name="toc-Description" href="#Description">1 Description</a></li>
  <li><a name="toc-Codec-Options" href="#Codec-Options">2 Codec Options</a></li>
  <li><a name="toc-Decoders" href="#Decoders">3 Decoders</a></li>
  <li><a name="toc-Video-Decoders" href="#Video-Decoders">4 Video Decoders</a>
  <ul class="no-bullet">
    <li><a name="toc-hevc" href="#hevc">4.1 hevc</a></li>
    <li><a name="toc-rawvideo" href="#rawvideo">4.2 rawvideo</a>
    <ul class="no-bullet">
      <li><a name="toc-Options" href="#Options">4.2.1 Options</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Audio-Decoders" href="#Audio-Decoders">5 Audio Decoders</a>
  <ul class="no-bullet">
    <li><a name="toc-ac3" href="#ac3">5.1 ac3</a>
    <ul class="no-bullet">
      <li><a name="toc-AC_002d3-Decoder-Options" href="#AC_002d3-Decoder-Options">5.1.1 AC-3 Decoder Options</a></li>
    </ul></li>
    <li><a name="toc-flac-1" href="#flac-1">5.2 flac</a>
    <ul class="no-bullet">
      <li><a name="toc-FLAC-Decoder-options" href="#FLAC-Decoder-options">5.2.1 FLAC Decoder options</a></li>
    </ul></li>
    <li><a name="toc-ffwavesynth" href="#ffwavesynth">5.3 ffwavesynth</a></li>
    <li><a name="toc-libcelt" href="#libcelt">5.4 libcelt</a></li>
    <li><a name="toc-libgsm" href="#libgsm">5.5 libgsm</a></li>
    <li><a name="toc-libilbc" href="#libilbc">5.6 libilbc</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-1" href="#Options-1">5.6.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libopencore_002damrnb" href="#libopencore_002damrnb">5.7 libopencore-amrnb</a></li>
    <li><a name="toc-libopencore_002damrwb" href="#libopencore_002damrwb">5.8 libopencore-amrwb</a></li>
    <li><a name="toc-libopus" href="#libopus">5.9 libopus</a></li>
  </ul></li>
  <li><a name="toc-Subtitles-Decoders" href="#Subtitles-Decoders">6 Subtitles Decoders</a>
  <ul class="no-bullet">
    <li><a name="toc-dvbsub" href="#dvbsub">6.1 dvbsub</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-2" href="#Options-2">6.1.1 Options</a></li>
    </ul></li>
    <li><a name="toc-dvdsub" href="#dvdsub">6.2 dvdsub</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-3" href="#Options-3">6.2.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libzvbi_002dteletext" href="#libzvbi_002dteletext">6.3 libzvbi-teletext</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-4" href="#Options-4">6.3.1 Options</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Encoders" href="#Encoders">7 Encoders</a></li>
  <li><a name="toc-Audio-Encoders" href="#Audio-Encoders">8 Audio Encoders</a>
  <ul class="no-bullet">
    <li><a name="toc-aac" href="#aac">8.1 aac</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-5" href="#Options-5">8.1.1 Options</a></li>
    </ul></li>
    <li><a name="toc-ac3-and-ac3_005ffixed" href="#ac3-and-ac3_005ffixed">8.2 ac3 and ac3_fixed</a>
    <ul class="no-bullet">
      <li><a name="toc-AC_002d3-Metadata" href="#AC_002d3-Metadata">8.2.1 AC-3 Metadata</a>
      <ul class="no-bullet">
        <li><a name="toc-Metadata-Control-Options" href="#Metadata-Control-Options">8.2.1.1 Metadata Control Options</a></li>
        <li><a name="toc-Downmix-Levels" href="#Downmix-Levels">8.2.1.2 Downmix Levels</a></li>
        <li><a name="toc-Audio-Production-Information" href="#Audio-Production-Information">8.2.1.3 Audio Production Information</a></li>
        <li><a name="toc-Other-Metadata-Options" href="#Other-Metadata-Options">8.2.1.4 Other Metadata Options</a></li>
      </ul></li>
      <li><a name="toc-Extended-Bitstream-Information" href="#Extended-Bitstream-Information">8.2.2 Extended Bitstream Information</a>
      <ul class="no-bullet">
        <li><a name="toc-Extended-Bitstream-Information-_002d-Part-1" href="#Extended-Bitstream-Information-_002d-Part-1">8.2.2.1 Extended Bitstream Information - Part 1</a></li>
        <li><a name="toc-Extended-Bitstream-Information-_002d-Part-2" href="#Extended-Bitstream-Information-_002d-Part-2">8.2.2.2 Extended Bitstream Information - Part 2</a></li>
      </ul></li>
      <li><a name="toc-Other-AC_002d3-Encoding-Options" href="#Other-AC_002d3-Encoding-Options">8.2.3 Other AC-3 Encoding Options</a></li>
      <li><a name="toc-Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options" href="#Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options">8.2.4 Floating-Point-Only AC-3 Encoding Options</a></li>
    </ul></li>
    <li><a name="toc-flac-2" href="#flac-2">8.3 flac</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-6" href="#Options-6">8.3.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libfaac-1" href="#libfaac-1">8.4 libfaac</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-7" href="#Options-7">8.4.1 Options</a></li>
      <li><a name="toc-Examples" href="#Examples">8.4.2 Examples</a></li>
    </ul></li>
    <li><a name="toc-libfdk_005faac" href="#libfdk_005faac">8.5 libfdk_aac</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-8" href="#Options-8">8.5.1 Options</a></li>
      <li><a name="toc-Examples-1" href="#Examples-1">8.5.2 Examples</a></li>
    </ul></li>
    <li><a name="toc-libmp3lame-1" href="#libmp3lame-1">8.6 libmp3lame</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-9" href="#Options-9">8.6.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libopencore_002damrnb-1" href="#libopencore_002damrnb-1">8.7 libopencore-amrnb</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-10" href="#Options-10">8.7.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libshine-1" href="#libshine-1">8.8 libshine</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-11" href="#Options-11">8.8.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libtwolame" href="#libtwolame">8.9 libtwolame</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-12" href="#Options-12">8.9.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libvo_002daacenc-1" href="#libvo_002daacenc-1">8.10 libvo-aacenc</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-13" href="#Options-13">8.10.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libvo_002damrwbenc" href="#libvo_002damrwbenc">8.11 libvo-amrwbenc</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-14" href="#Options-14">8.11.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libopus-1" href="#libopus-1">8.12 libopus</a>
    <ul class="no-bullet">
      <li><a name="toc-Option-Mapping" href="#Option-Mapping">8.12.1 Option Mapping</a></li>
    </ul></li>
    <li><a name="toc-libvorbis" href="#libvorbis">8.13 libvorbis</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-15" href="#Options-15">8.13.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libwavpack-1" href="#libwavpack-1">8.14 libwavpack</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-16" href="#Options-16">8.14.1 Options</a></li>
    </ul></li>
    <li><a name="toc-wavpack" href="#wavpack">8.15 wavpack</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-17" href="#Options-17">8.15.1 Options</a>
      <ul class="no-bullet">
        <li><a name="toc-Shared-options" href="#Shared-options">8.15.1.1 Shared options</a></li>
        <li><a name="toc-Private-options" href="#Private-options">8.15.1.2 Private options</a></li>
      </ul></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Video-Encoders" href="#Video-Encoders">9 Video Encoders</a>
  <ul class="no-bullet">
    <li><a name="toc-libopenh264" href="#libopenh264">9.1 libopenh264</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-18" href="#Options-18">9.1.1 Options</a></li>
    </ul></li>
    <li><a name="toc-jpeg2000" href="#jpeg2000">9.2 jpeg2000</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-19" href="#Options-19">9.2.1 Options</a></li>
    </ul></li>
    <li><a name="toc-snow" href="#snow">9.3 snow</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-20" href="#Options-20">9.3.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libtheora" href="#libtheora">9.4 libtheora</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-21" href="#Options-21">9.4.1 Options</a></li>
      <li><a name="toc-Examples-2" href="#Examples-2">9.4.2 Examples</a></li>
    </ul></li>
    <li><a name="toc-libvpx" href="#libvpx">9.5 libvpx</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-22" href="#Options-22">9.5.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libwebp" href="#libwebp">9.6 libwebp</a>
    <ul class="no-bullet">
      <li><a name="toc-Pixel-Format" href="#Pixel-Format">9.6.1 Pixel Format</a></li>
      <li><a name="toc-Options-23" href="#Options-23">9.6.2 Options</a></li>
    </ul></li>
    <li><a name="toc-libx264_002c-libx264rgb" href="#libx264_002c-libx264rgb">9.7 libx264, libx264rgb</a>
    <ul class="no-bullet">
      <li><a name="toc-Supported-Pixel-Formats" href="#Supported-Pixel-Formats">9.7.1 Supported Pixel Formats</a></li>
      <li><a name="toc-Options-24" href="#Options-24">9.7.2 Options</a></li>
    </ul></li>
    <li><a name="toc-libx265" href="#libx265">9.8 libx265</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-25" href="#Options-25">9.8.1 Options</a></li>
    </ul></li>
    <li><a name="toc-libxvid" href="#libxvid">9.9 libxvid</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-26" href="#Options-26">9.9.1 Options</a></li>
    </ul></li>
    <li><a name="toc-mpeg2" href="#mpeg2">9.10 mpeg2</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-27" href="#Options-27">9.10.1 Options</a></li>
    </ul></li>
    <li><a name="toc-png" href="#png">9.11 png</a>
    <ul class="no-bullet">
      <li><a name="toc-Private-options-1" href="#Private-options-1">9.11.1 Private options</a></li>
    </ul></li>
    <li><a name="toc-ProRes" href="#ProRes">9.12 ProRes</a>
    <ul class="no-bullet">
      <li><a name="toc-Private-Options-for-prores_002dks" href="#Private-Options-for-prores_002dks">9.12.1 Private Options for prores-ks</a></li>
      <li><a name="toc-Speed-considerations" href="#Speed-considerations">9.12.2 Speed considerations</a></li>
    </ul></li>
    <li><a name="toc-libkvazaar" href="#libkvazaar">9.13 libkvazaar</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-28" href="#Options-28">9.13.1 Options</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-Subtitles-Encoders" href="#Subtitles-Encoders">10 Subtitles Encoders</a>
  <ul class="no-bullet">
    <li><a name="toc-dvdsub-1" href="#dvdsub-1">10.1 dvdsub</a>
    <ul class="no-bullet">
      <li><a name="toc-Options-29" href="#Options-29">10.1.1 Options</a></li>
    </ul></li>
  </ul></li>
  <li><a name="toc-See-Also" href="#See-Also">11 See Also</a></li>
  <li><a name="toc-Authors" href="#Authors">12 Authors</a></li>
</ul>
</div>


<a name="Description"></a>
<h2 class="chapter">1 Description<span class="pull-right"><a class="anchor hidden-xs" href="#Description" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Description" aria-hidden="true">TOC</a></span></h2>

<p>This document describes the codecs (decoders and encoders) provided by
the libavcodec library.
</p>

<a name="codec_002doptions"></a><a name="Codec-Options"></a>
<h2 class="chapter">2 Codec Options<span class="pull-right"><a class="anchor hidden-xs" href="#Codec-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Codec-Options" aria-hidden="true">TOC</a></span></h2>

<p>libavcodec provides some generic global options, which can be set on
all the encoders and decoders. In addition each codec may support
so-called private options, which are specific for a given codec.
</p>
<p>Sometimes, a global option may only affect a specific kind of codec,
and may be nonsensical or ignored by another, so you need to be aware
of the meaning of the specified options. Also some options are
meant only for decoding or encoding.
</p>
<p>Options may be set by specifying -<var>option</var> <var>value</var> in the
FFmpeg tools, or by setting the value explicitly in the
<code>AVCodecContext</code> options or using the <samp>libavutil/opt.h</samp> API
for programmatic use.
</p>
<p>The list of supported options follow:
</p>
<dl compact="compact">
<dt><samp>b <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd><p>Set bitrate in bits/s. Default value is 200K.
</p>
</dd>
<dt><samp>ab <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dd><p>Set audio bitrate (in bits/s). Default value is 128K.
</p>
</dd>
<dt><samp>bt <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate
tolerance specifies how far ratecontrol is willing to deviate from the
target average bitrate value. This is not related to min/max
bitrate. Lowering tolerance too much has an adverse effect on quality.
</p>
</dd>
<dt><samp>flags <var>flags</var> (<em>decoding/encoding,audio,video,subtitles</em>)</samp></dt>
<dd><p>Set generic flags.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>mv4</samp>&rsquo;</dt>
<dd><p>Use four motion vector by macroblock (mpeg4).
</p></dd>
<dt>&lsquo;<samp>qpel</samp>&rsquo;</dt>
<dd><p>Use 1/4 pel motion compensation.
</p></dd>
<dt>&lsquo;<samp>loop</samp>&rsquo;</dt>
<dd><p>Use loop filter.
</p></dd>
<dt>&lsquo;<samp>qscale</samp>&rsquo;</dt>
<dd><p>Use fixed qscale.
</p></dd>
<dt>&lsquo;<samp>gmc</samp>&rsquo;</dt>
<dd><p>Use gmc.
</p></dd>
<dt>&lsquo;<samp>mv0</samp>&rsquo;</dt>
<dd><p>Always try a mb with mv=&lt;0,0&gt;.
</p></dd>
<dt>&lsquo;<samp>input_preserved</samp>&rsquo;</dt>
<dt>&lsquo;<samp>pass1</samp>&rsquo;</dt>
<dd><p>Use internal 2pass ratecontrol in first pass mode.
</p></dd>
<dt>&lsquo;<samp>pass2</samp>&rsquo;</dt>
<dd><p>Use internal 2pass ratecontrol in second pass mode.
</p></dd>
<dt>&lsquo;<samp>gray</samp>&rsquo;</dt>
<dd><p>Only decode/encode grayscale.
</p></dd>
<dt>&lsquo;<samp>emu_edge</samp>&rsquo;</dt>
<dd><p>Do not draw edges.
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>Set error[?] variables during encoding.
</p></dd>
<dt>&lsquo;<samp>truncated</samp>&rsquo;</dt>
<dt>&lsquo;<samp>naq</samp>&rsquo;</dt>
<dd><p>Normalize adaptive quantization.
</p></dd>
<dt>&lsquo;<samp>ildct</samp>&rsquo;</dt>
<dd><p>Use interlaced DCT.
</p></dd>
<dt>&lsquo;<samp>low_delay</samp>&rsquo;</dt>
<dd><p>Force low delay.
</p></dd>
<dt>&lsquo;<samp>global_header</samp>&rsquo;</dt>
<dd><p>Place global headers in extradata instead of every keyframe.
</p></dd>
<dt>&lsquo;<samp>bitexact</samp>&rsquo;</dt>
<dd><p>Only write platform-, build- and time-independent data. (except (I)DCT).
This ensures that file and data checksums are reproducible and match between
platforms. Its primary use is for regression testing.
</p></dd>
<dt>&lsquo;<samp>aic</samp>&rsquo;</dt>
<dd><p>Apply H263 advanced intra coding / mpeg4 ac prediction.
</p></dd>
<dt>&lsquo;<samp>cbp</samp>&rsquo;</dt>
<dd><p>Deprecated, use mpegvideo private options instead.
</p></dd>
<dt>&lsquo;<samp>qprd</samp>&rsquo;</dt>
<dd><p>Deprecated, use mpegvideo private options instead.
</p></dd>
<dt>&lsquo;<samp>ilme</samp>&rsquo;</dt>
<dd><p>Apply interlaced motion estimation.
</p></dd>
<dt>&lsquo;<samp>cgop</samp>&rsquo;</dt>
<dd><p>Use closed gop.
</p></dd>
</dl>

</dd>
<dt><samp>me_method <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set motion estimation method.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>zero motion estimation (fastest)
</p></dd>
<dt>&lsquo;<samp>full</samp>&rsquo;</dt>
<dd><p>full motion estimation (slowest)
</p></dd>
<dt>&lsquo;<samp>epzs</samp>&rsquo;</dt>
<dd><p>EPZS motion estimation (default)
</p></dd>
<dt>&lsquo;<samp>esa</samp>&rsquo;</dt>
<dd><p>esa motion estimation (alias for full)
</p></dd>
<dt>&lsquo;<samp>tesa</samp>&rsquo;</dt>
<dd><p>tesa motion estimation
</p></dd>
<dt>&lsquo;<samp>dia</samp>&rsquo;</dt>
<dd><p>dia motion estimation (alias for epzs)
</p></dd>
<dt>&lsquo;<samp>log</samp>&rsquo;</dt>
<dd><p>log motion estimation
</p></dd>
<dt>&lsquo;<samp>phods</samp>&rsquo;</dt>
<dd><p>phods motion estimation
</p></dd>
<dt>&lsquo;<samp>x1</samp>&rsquo;</dt>
<dd><p>X1 motion estimation
</p></dd>
<dt>&lsquo;<samp>hex</samp>&rsquo;</dt>
<dd><p>hex motion estimation
</p></dd>
<dt>&lsquo;<samp>umh</samp>&rsquo;</dt>
<dd><p>umh motion estimation
</p></dd>
<dt>&lsquo;<samp>iter</samp>&rsquo;</dt>
<dd><p>iter motion estimation
</p></dd>
</dl>

</dd>
<dt><samp>extradata_size <var>integer</var></samp></dt>
<dd><p>Set extradata size.
</p>
</dd>
<dt><samp>time_base <var>rational number</var></samp></dt>
<dd><p>Set codec time base.
</p>
<p>It is the fundamental unit of time (in seconds) in terms of which
frame timestamps are represented. For fixed-fps content, timebase
should be <code>1 / frame_rate</code> and timestamp increments should be
identically 1.
</p>
</dd>
<dt><samp>g <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set the group of picture (GOP) size. Default value is 12.
</p>
</dd>
<dt><samp>ar <var>integer</var> (<em>decoding/encoding,audio</em>)</samp></dt>
<dd><p>Set audio sampling rate (in Hz).
</p>
</dd>
<dt><samp>ac <var>integer</var> (<em>decoding/encoding,audio</em>)</samp></dt>
<dd><p>Set number of audio channels.
</p>
</dd>
<dt><samp>cutoff <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dd><p>Set cutoff bandwidth.
</p>
</dd>
<dt><samp>frame_size <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dd><p>Set audio frame size.
</p>
<p>Each submitted frame except the last must contain exactly frame_size
samples per channel. May be 0 when the codec has
CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is not
restricted. It is set by some decoders to indicate constant frame
size.
</p>
</dd>
<dt><samp>frame_number <var>integer</var></samp></dt>
<dd><p>Set the frame number.
</p>
</dd>
<dt><samp>delay <var>integer</var></samp></dt>
<dt><samp>qcomp <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set video quantizer scale compression (VBR). It is used as a constant
in the ratecontrol equation. Recommended range for default rc_eq:
0.0-1.0.
</p>
</dd>
<dt><samp>qblur <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set video quantizer scale blur (VBR).
</p>
</dd>
<dt><samp>qmin <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set min video quantizer scale (VBR). Must be included between -1 and
69, default value is 2.
</p>
</dd>
<dt><samp>qmax <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set max video quantizer scale (VBR). Must be included between -1 and
1024, default value is 31.
</p>
</dd>
<dt><samp>qdiff <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set max difference between the quantizer scale (VBR).
</p>
</dd>
<dt><samp>bf <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set max number of B frames between non-B-frames.
</p>
<p>Must be an integer between -1 and 16. 0 means that B-frames are
disabled. If a value of -1 is used, it will choose an automatic value
depending on the encoder.
</p>
<p>Default value is 0.
</p>
</dd>
<dt><samp>b_qfactor <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set qp factor between P and B frames.
</p>
</dd>
<dt><samp>rc_strategy <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set ratecontrol method.
</p>
</dd>
<dt><samp>b_strategy <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set strategy to choose between I/P/B-frames.
</p>
</dd>
<dt><samp>ps <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set RTP payload size in bytes.
</p>
</dd>
<dt><samp>mv_bits <var>integer</var></samp></dt>
<dt><samp>header_bits <var>integer</var></samp></dt>
<dt><samp>i_tex_bits <var>integer</var></samp></dt>
<dt><samp>p_tex_bits <var>integer</var></samp></dt>
<dt><samp>i_count <var>integer</var></samp></dt>
<dt><samp>p_count <var>integer</var></samp></dt>
<dt><samp>skip_count <var>integer</var></samp></dt>
<dt><samp>misc_bits <var>integer</var></samp></dt>
<dt><samp>frame_bits <var>integer</var></samp></dt>
<dt><samp>codec_tag <var>integer</var></samp></dt>
<dt><samp>bug <var>flags</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Workaround not auto detected encoder bugs.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>autodetect</samp>&rsquo;</dt>
<dt>&lsquo;<samp>old_msmpeg4</samp>&rsquo;</dt>
<dd><p>some old lavc generated msmpeg4v3 files (no autodetection)
</p></dd>
<dt>&lsquo;<samp>xvid_ilace</samp>&rsquo;</dt>
<dd><p>Xvid interlacing bug (autodetected if fourcc==XVIX)
</p></dd>
<dt>&lsquo;<samp>ump4</samp>&rsquo;</dt>
<dd><p>(autodetected if fourcc==UMP4)
</p></dd>
<dt>&lsquo;<samp>no_padding</samp>&rsquo;</dt>
<dd><p>padding bug (autodetected)
</p></dd>
<dt>&lsquo;<samp>amv</samp>&rsquo;</dt>
<dt>&lsquo;<samp>ac_vlc</samp>&rsquo;</dt>
<dd><p>illegal vlc bug (autodetected per fourcc)
</p></dd>
<dt>&lsquo;<samp>qpel_chroma</samp>&rsquo;</dt>
<dt>&lsquo;<samp>std_qpel</samp>&rsquo;</dt>
<dd><p>old standard qpel (autodetected per fourcc/version)
</p></dd>
<dt>&lsquo;<samp>qpel_chroma2</samp>&rsquo;</dt>
<dt>&lsquo;<samp>direct_blocksize</samp>&rsquo;</dt>
<dd><p>direct-qpel-blocksize bug (autodetected per fourcc/version)
</p></dd>
<dt>&lsquo;<samp>edge</samp>&rsquo;</dt>
<dd><p>edge padding bug (autodetected per fourcc/version)
</p></dd>
<dt>&lsquo;<samp>hpel_chroma</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dc_clip</samp>&rsquo;</dt>
<dt>&lsquo;<samp>ms</samp>&rsquo;</dt>
<dd><p>Workaround various bugs in microsoft broken decoders.
</p></dd>
<dt>&lsquo;<samp>trunc</samp>&rsquo;</dt>
<dd><p>trancated frames
</p></dd>
</dl>

</dd>
<dt><samp>lelim <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set single coefficient elimination threshold for luminance (negative
values also consider DC coefficient).
</p>
</dd>
<dt><samp>celim <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set single coefficient elimination threshold for chrominance (negative
values also consider dc coefficient)
</p>
</dd>
<dt><samp>strict <var>integer</var> (<em>decoding/encoding,audio,video</em>)</samp></dt>
<dd><p>Specify how strictly to follow the standards.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>very</samp>&rsquo;</dt>
<dd><p>strictly conform to a older more strict version of the spec or reference software
</p></dd>
<dt>&lsquo;<samp>strict</samp>&rsquo;</dt>
<dd><p>strictly conform to all the things in the spec no matter what consequences
</p></dd>
<dt>&lsquo;<samp>normal</samp>&rsquo;</dt>
<dt>&lsquo;<samp>unofficial</samp>&rsquo;</dt>
<dd><p>allow unofficial extensions
</p></dd>
<dt>&lsquo;<samp>experimental</samp>&rsquo;</dt>
<dd><p>allow non standardized experimental things, experimental
(unfinished/work in progress/not well tested) decoders and encoders.
Note: experimental decoders can pose a security risk, do not use this for
decoding untrusted input.
</p></dd>
</dl>

</dd>
<dt><samp>b_qoffset <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set QP offset between P and B frames.
</p>
</dd>
<dt><samp>err_detect <var>flags</var> (<em>decoding,audio,video</em>)</samp></dt>
<dd><p>Set error detection flags.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>crccheck</samp>&rsquo;</dt>
<dd><p>verify embedded CRCs
</p></dd>
<dt>&lsquo;<samp>bitstream</samp>&rsquo;</dt>
<dd><p>detect bitstream specification deviations
</p></dd>
<dt>&lsquo;<samp>buffer</samp>&rsquo;</dt>
<dd><p>detect improper bitstream length
</p></dd>
<dt>&lsquo;<samp>explode</samp>&rsquo;</dt>
<dd><p>abort decoding on minor error detection
</p></dd>
<dt>&lsquo;<samp>ignore_err</samp>&rsquo;</dt>
<dd><p>ignore decoding errors, and continue decoding.
This is useful if you want to analyze the content of a video and thus want
everything to be decoded no matter what. This option will not result in a video
that is pleasing to watch in case of errors.
</p></dd>
<dt>&lsquo;<samp>careful</samp>&rsquo;</dt>
<dd><p>consider things that violate the spec and have not been seen in the wild as errors
</p></dd>
<dt>&lsquo;<samp>compliant</samp>&rsquo;</dt>
<dd><p>consider all spec non compliancies as errors
</p></dd>
<dt>&lsquo;<samp>aggressive</samp>&rsquo;</dt>
<dd><p>consider things that a sane encoder should not do as an error
</p></dd>
</dl>

</dd>
<dt><samp>has_b_frames <var>integer</var></samp></dt>
<dt><samp>block_align <var>integer</var></samp></dt>
<dt><samp>mpeg_quant <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Use MPEG quantizers instead of H.263.
</p>
</dd>
<dt><samp>qsquish <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>How to keep quantizer between qmin and qmax (0 = clip, 1 = use
differentiable function).
</p>
</dd>
<dt><samp>rc_qmod_amp <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set experimental quantizer modulation.
</p>
</dd>
<dt><samp>rc_qmod_freq <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set experimental quantizer modulation.
</p>
</dd>
<dt><samp>rc_override_count <var>integer</var></samp></dt>
<dt><samp>rc_eq <var>string</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set rate control equation. When computing the expression, besides the
standard functions defined in the section &rsquo;Expression Evaluation&rsquo;, the
following functions are available: bits2qp(bits), qp2bits(qp). Also
the following constants are available: iTex pTex tex mv fCode iCount
mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex
avgTex.
</p>
</dd>
<dt><samp>maxrate <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd><p>Set max bitrate tolerance (in bits/s). Requires bufsize to be set.
</p>
</dd>
<dt><samp>minrate <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd><p>Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR
encode. It is of little use elsewise.
</p>
</dd>
<dt><samp>bufsize <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd><p>Set ratecontrol buffer size (in bits).
</p>
</dd>
<dt><samp>rc_buf_aggressivity <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Currently useless.
</p>
</dd>
<dt><samp>i_qfactor <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set QP factor between P and I frames.
</p>
</dd>
<dt><samp>i_qoffset <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set QP offset between P and I frames.
</p>
</dd>
<dt><samp>rc_init_cplx <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set initial complexity for 1-pass encoding.
</p>
</dd>
<dt><samp>dct <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set DCT algorithm.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>autoselect a good one (default)
</p></dd>
<dt>&lsquo;<samp>fastint</samp>&rsquo;</dt>
<dd><p>fast integer
</p></dd>
<dt>&lsquo;<samp>int</samp>&rsquo;</dt>
<dd><p>accurate integer
</p></dd>
<dt>&lsquo;<samp>mmx</samp>&rsquo;</dt>
<dt>&lsquo;<samp>altivec</samp>&rsquo;</dt>
<dt>&lsquo;<samp>faan</samp>&rsquo;</dt>
<dd><p>floating point AAN DCT
</p></dd>
</dl>

</dd>
<dt><samp>lumi_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Compress bright areas stronger than medium ones.
</p>
</dd>
<dt><samp>tcplx_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set temporal complexity masking.
</p>
</dd>
<dt><samp>scplx_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set spatial complexity masking.
</p>
</dd>
<dt><samp>p_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set inter masking.
</p>
</dd>
<dt><samp>dark_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Compress dark areas stronger than medium ones.
</p>
</dd>
<dt><samp>idct <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dd><p>Select IDCT implementation.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dt>&lsquo;<samp>int</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simple</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simplemmx</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simpleauto</samp>&rsquo;</dt>
<dd><p>Automatically pick a IDCT compatible with the simple one
</p>
</dd>
<dt>&lsquo;<samp>arm</samp>&rsquo;</dt>
<dt>&lsquo;<samp>altivec</samp>&rsquo;</dt>
<dt>&lsquo;<samp>sh4</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simplearm</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simplearmv5te</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simplearmv6</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simpleneon</samp>&rsquo;</dt>
<dt>&lsquo;<samp>simplealpha</samp>&rsquo;</dt>
<dt>&lsquo;<samp>ipp</samp>&rsquo;</dt>
<dt>&lsquo;<samp>xvidmmx</samp>&rsquo;</dt>
<dt>&lsquo;<samp>faani</samp>&rsquo;</dt>
<dd><p>floating point AAN IDCT
</p></dd>
</dl>

</dd>
<dt><samp>slice_count <var>integer</var></samp></dt>
<dt><samp>ec <var>flags</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Set error concealment strategy.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>guess_mvs</samp>&rsquo;</dt>
<dd><p>iterative motion vector (MV) search (slow)
</p></dd>
<dt>&lsquo;<samp>deblock</samp>&rsquo;</dt>
<dd><p>use strong deblock filter for damaged MBs
</p></dd>
<dt>&lsquo;<samp>favor_inter</samp>&rsquo;</dt>
<dd><p>favor predicting from the previous frame instead of the current
</p></dd>
</dl>

</dd>
<dt><samp>bits_per_coded_sample <var>integer</var></samp></dt>
<dt><samp>pred <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set prediction method.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>left</samp>&rsquo;</dt>
<dt>&lsquo;<samp>plane</samp>&rsquo;</dt>
<dt>&lsquo;<samp>median</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>aspect <var>rational number</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set sample aspect ratio.
</p>
</dd>
<dt><samp>debug <var>flags</var> (<em>decoding/encoding,audio,video,subtitles</em>)</samp></dt>
<dd><p>Print specific debug info.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>pict</samp>&rsquo;</dt>
<dd><p>picture info
</p></dd>
<dt>&lsquo;<samp>rc</samp>&rsquo;</dt>
<dd><p>rate control
</p></dd>
<dt>&lsquo;<samp>bitstream</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mb_type</samp>&rsquo;</dt>
<dd><p>macroblock (MB) type
</p></dd>
<dt>&lsquo;<samp>qp</samp>&rsquo;</dt>
<dd><p>per-block quantization parameter (QP)
</p></dd>
<dt>&lsquo;<samp>mv</samp>&rsquo;</dt>
<dd><p>motion vector
</p></dd>
<dt>&lsquo;<samp>dct_coeff</samp>&rsquo;</dt>
<dt>&lsquo;<samp>green_metadata</samp>&rsquo;</dt>
<dd><p>display complexity metadata for the upcoming frame, GoP or for a given duration.
</p>
</dd>
<dt>&lsquo;<samp>skip</samp>&rsquo;</dt>
<dt>&lsquo;<samp>startcode</samp>&rsquo;</dt>
<dt>&lsquo;<samp>pts</samp>&rsquo;</dt>
<dt>&lsquo;<samp>er</samp>&rsquo;</dt>
<dd><p>error recognition
</p></dd>
<dt>&lsquo;<samp>mmco</samp>&rsquo;</dt>
<dd><p>memory management control operations (H.264)
</p></dd>
<dt>&lsquo;<samp>bugs</samp>&rsquo;</dt>
<dt>&lsquo;<samp>vis_qp</samp>&rsquo;</dt>
<dd><p>visualize quantization parameter (QP), lower QP are tinted greener
</p></dd>
<dt>&lsquo;<samp>vis_mb_type</samp>&rsquo;</dt>
<dd><p>visualize block types
</p></dd>
<dt>&lsquo;<samp>buffers</samp>&rsquo;</dt>
<dd><p>picture buffer allocations
</p></dd>
<dt>&lsquo;<samp>thread_ops</samp>&rsquo;</dt>
<dd><p>threading operations
</p></dd>
<dt>&lsquo;<samp>nomc</samp>&rsquo;</dt>
<dd><p>skip motion compensation
</p></dd>
</dl>

</dd>
<dt><samp>vismv <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Visualize motion vectors (MVs).
</p>
<p>This option is deprecated, see the codecview filter instead.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>pf</samp>&rsquo;</dt>
<dd><p>forward predicted MVs of P-frames
</p></dd>
<dt>&lsquo;<samp>bf</samp>&rsquo;</dt>
<dd><p>forward predicted MVs of B-frames
</p></dd>
<dt>&lsquo;<samp>bb</samp>&rsquo;</dt>
<dd><p>backward predicted MVs of B-frames
</p></dd>
</dl>

</dd>
<dt><samp>cmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set full pel me compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>subcmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set sub pel me compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>mbcmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set macroblock compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>ildctcmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set interlaced dct compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>dia_size <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set diamond type &amp; size for motion estimation.
</p>
</dd>
<dt><samp>last_pred <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set amount of motion predictors from the previous frame.
</p>
</dd>
<dt><samp>preme <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set pre motion estimation.
</p>
</dd>
<dt><samp>precmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set pre motion estimation compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>pre_dia_size <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set diamond type &amp; size for motion estimation pre-pass.
</p>
</dd>
<dt><samp>subq <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set sub pel motion estimation quality.
</p>
</dd>
<dt><samp>dtg_active_format <var>integer</var></samp></dt>
<dt><samp>me_range <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set limit motion vectors range (1023 for DivX player).
</p>
</dd>
<dt><samp>ibias <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set intra quant bias.
</p>
</dd>
<dt><samp>pbias <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set inter quant bias.
</p>
</dd>
<dt><samp>color_table_id <var>integer</var></samp></dt>
<dt><samp>global_quality <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dt><samp>coder <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>vlc</samp>&rsquo;</dt>
<dd><p>variable length coder / huffman coder
</p></dd>
<dt>&lsquo;<samp>ac</samp>&rsquo;</dt>
<dd><p>arithmetic coder
</p></dd>
<dt>&lsquo;<samp>raw</samp>&rsquo;</dt>
<dd><p>raw (no encoding)
</p></dd>
<dt>&lsquo;<samp>rle</samp>&rsquo;</dt>
<dd><p>run-length coder
</p></dd>
<dt>&lsquo;<samp>deflate</samp>&rsquo;</dt>
<dd><p>deflate-based coder
</p></dd>
</dl>

</dd>
<dt><samp>context <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set context model.
</p>
</dd>
<dt><samp>slice_flags <var>integer</var></samp></dt>
<dt><samp>xvmc_acceleration <var>integer</var></samp></dt>
<dt><samp>mbd <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set macroblock decision algorithm (high quality mode).
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>simple</samp>&rsquo;</dt>
<dd><p>use mbcmp (default)
</p></dd>
<dt>&lsquo;<samp>bits</samp>&rsquo;</dt>
<dd><p>use fewest bits
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>use best rate distortion
</p></dd>
</dl>

</dd>
<dt><samp>stream_codec_tag <var>integer</var></samp></dt>
<dt><samp>sc_threshold <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set scene change threshold.
</p>
</dd>
<dt><samp>lmin <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set min lagrange factor (VBR).
</p>
</dd>
<dt><samp>lmax <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set max lagrange factor (VBR).
</p>
</dd>
<dt><samp>nr <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set noise reduction.
</p>
</dd>
<dt><samp>rc_init_occupancy <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set number of bits which should be loaded into the rc buffer before
decoding starts.
</p>
</dd>
<dt><samp>flags2 <var>flags</var> (<em>decoding/encoding,audio,video</em>)</samp></dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>fast</samp>&rsquo;</dt>
<dd><p>Allow non spec compliant speedup tricks.
</p></dd>
<dt>&lsquo;<samp>sgop</samp>&rsquo;</dt>
<dd><p>Deprecated, use mpegvideo private options instead.
</p></dd>
<dt>&lsquo;<samp>noout</samp>&rsquo;</dt>
<dd><p>Skip bitstream encoding.
</p></dd>
<dt>&lsquo;<samp>ignorecrop</samp>&rsquo;</dt>
<dd><p>Ignore cropping information from sps.
</p></dd>
<dt>&lsquo;<samp>local_header</samp>&rsquo;</dt>
<dd><p>Place global headers at every keyframe instead of in extradata.
</p></dd>
<dt>&lsquo;<samp>chunks</samp>&rsquo;</dt>
<dd><p>Frame data might be split into multiple chunks.
</p></dd>
<dt>&lsquo;<samp>showall</samp>&rsquo;</dt>
<dd><p>Show all frames before the first keyframe.
</p></dd>
<dt>&lsquo;<samp>skiprd</samp>&rsquo;</dt>
<dd><p>Deprecated, use mpegvideo private options instead.
</p></dd>
<dt>&lsquo;<samp>export_mvs</samp>&rsquo;</dt>
<dd><p>Export motion vectors into frame side-data (see <code>AV_FRAME_DATA_MOTION_VECTORS</code>)
for codecs that support it. See also <samp>doc/examples/export_mvs.c</samp>.
</p></dd>
</dl>

</dd>
<dt><samp>error <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dt><samp>qns <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Deprecated, use mpegvideo private options instead.
</p>
</dd>
<dt><samp>threads <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dd><p>Set the number of threads to be used, in case the selected codec
implementation supports multi-threading.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>auto, 0</samp>&rsquo;</dt>
<dd><p>automatically select the number of threads to set
</p></dd>
</dl>

<p>Default value is &lsquo;<samp>auto</samp>&rsquo;.
</p>
</dd>
<dt><samp>me_threshold <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set motion estimation threshold.
</p>
</dd>
<dt><samp>mb_threshold <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set macroblock threshold.
</p>
</dd>
<dt><samp>dc <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set intra_dc_precision.
</p>
</dd>
<dt><samp>nssew <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set nsse weight.
</p>
</dd>
<dt><samp>skip_top <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Set number of macroblock rows at the top which are skipped.
</p>
</dd>
<dt><samp>skip_bottom <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Set number of macroblock rows at the bottom which are skipped.
</p>
</dd>
<dt><samp>profile <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>unknown</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_main</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_low</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_ssr</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_ltp</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_he</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_he_v2</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_ld</samp>&rsquo;</dt>
<dt>&lsquo;<samp>aac_eld</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg2_aac_low</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg2_aac_he</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg4_sp</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg4_core</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg4_main</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mpeg4_asp</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dts</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dts_es</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dts_96_24</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dts_hd_hra</samp>&rsquo;</dt>
<dt>&lsquo;<samp>dts_hd_ma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>level <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>unknown</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>lowres <var>integer</var> (<em>decoding,audio,video</em>)</samp></dt>
<dd><p>Decode at 1= 1/2, 2=1/4, 3=1/8 resolutions.
</p>
</dd>
<dt><samp>skip_threshold <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set frame skip threshold.
</p>
</dd>
<dt><samp>skip_factor <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set frame skip factor.
</p>
</dd>
<dt><samp>skip_exp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set frame skip exponent.
Negative values behave identical to the corresponding positive ones, except
that the score is normalized.
Positive values exist primarily for compatibility reasons and are not so useful.
</p>
</dd>
<dt><samp>skipcmp <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set frame skip compare function.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>sum of absolute differences, fast (default)
</p></dd>
<dt>&lsquo;<samp>sse</samp>&rsquo;</dt>
<dd><p>sum of squared errors
</p></dd>
<dt>&lsquo;<samp>satd</samp>&rsquo;</dt>
<dd><p>sum of absolute Hadamard transformed differences
</p></dd>
<dt>&lsquo;<samp>dct</samp>&rsquo;</dt>
<dd><p>sum of absolute DCT transformed differences
</p></dd>
<dt>&lsquo;<samp>psnr</samp>&rsquo;</dt>
<dd><p>sum of squared quantization errors (avoid, low quality)
</p></dd>
<dt>&lsquo;<samp>bit</samp>&rsquo;</dt>
<dd><p>number of bits needed for the block
</p></dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>rate distortion optimal, slow
</p></dd>
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>0
</p></dd>
<dt>&lsquo;<samp>vsad</samp>&rsquo;</dt>
<dd><p>sum of absolute vertical differences
</p></dd>
<dt>&lsquo;<samp>vsse</samp>&rsquo;</dt>
<dd><p>sum of squared vertical differences
</p></dd>
<dt>&lsquo;<samp>nsse</samp>&rsquo;</dt>
<dd><p>noise preserving sum of squared differences
</p></dd>
<dt>&lsquo;<samp>w53</samp>&rsquo;</dt>
<dd><p>5/3 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>w97</samp>&rsquo;</dt>
<dd><p>9/7 wavelet, only used in snow
</p></dd>
<dt>&lsquo;<samp>dctmax</samp>&rsquo;</dt>
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>border_mask <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Increase the quantizer for macroblocks close to borders.
</p>
</dd>
<dt><samp>mblmin <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set min macroblock lagrange factor (VBR).
</p>
</dd>
<dt><samp>mblmax <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set max macroblock lagrange factor (VBR).
</p>
</dd>
<dt><samp>mepc <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set motion estimation bitrate penalty compensation (1.0 = 256).
</p>
</dd>
<dt><samp>skip_loop_filter <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dt><samp>skip_idct        <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dt><samp>skip_frame       <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dd>
<p>Make decoder discard processing depending on the frame type selected
by the option value.
</p>
<p><samp>skip_loop_filter</samp> skips frame loop filtering, <samp>skip_idct</samp>
skips frame IDCT/dequantization, <samp>skip_frame</samp> skips decoding.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>none</samp>&rsquo;</dt>
<dd><p>Discard no frame.
</p>
</dd>
<dt>&lsquo;<samp>default</samp>&rsquo;</dt>
<dd><p>Discard useless frames like 0-sized frames.
</p>
</dd>
<dt>&lsquo;<samp>noref</samp>&rsquo;</dt>
<dd><p>Discard all non-reference frames.
</p>
</dd>
<dt>&lsquo;<samp>bidir</samp>&rsquo;</dt>
<dd><p>Discard all bidirectional frames.
</p>
</dd>
<dt>&lsquo;<samp>nokey</samp>&rsquo;</dt>
<dd><p>Discard all frames excepts keyframes.
</p>
</dd>
<dt>&lsquo;<samp>all</samp>&rsquo;</dt>
<dd><p>Discard all frames.
</p></dd>
</dl>

<p>Default value is &lsquo;<samp>default</samp>&rsquo;.
</p>
</dd>
<dt><samp>bidir_refine <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Refine the two motion vectors used in bidirectional macroblocks.
</p>
</dd>
<dt><samp>brd_scale <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Downscale frames for dynamic B-frame decision.
</p>
</dd>
<dt><samp>keyint_min <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set minimum interval between IDR-frames.
</p>
</dd>
<dt><samp>refs <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set reference frames to consider for motion compensation.
</p>
</dd>
<dt><samp>chromaoffset <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set chroma qp offset from luma.
</p>
</dd>
<dt><samp>trellis <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dd><p>Set rate-distortion optimal quantization.
</p>
</dd>
<dt><samp>sc_factor <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set value multiplied by qscale for each frame and added to
scene_change_score.
</p>
</dd>
<dt><samp>mv0_threshold <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dt><samp>b_sensitivity <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Adjust sensitivity of b_frame_strategy 1.
</p>
</dd>
<dt><samp>compression_level <var>integer</var> (<em>encoding,audio,video</em>)</samp></dt>
<dt><samp>min_prediction_order <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dt><samp>max_prediction_order <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dt><samp>timecode_frame_start <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Set GOP timecode frame start number, in non drop frame format.
</p>
</dd>
<dt><samp>request_channels <var>integer</var> (<em>decoding,audio</em>)</samp></dt>
<dd><p>Set desired number of audio channels.
</p>
</dd>
<dt><samp>bits_per_raw_sample <var>integer</var></samp></dt>
<dt><samp>channel_layout <var>integer</var> (<em>decoding/encoding,audio</em>)</samp></dt>
<dd>
<p>Possible values:
</p></dd>
<dt><samp>request_channel_layout <var>integer</var> (<em>decoding,audio</em>)</samp></dt>
<dd>
<p>Possible values:
</p></dd>
<dt><samp>rc_max_vbv_use <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dt><samp>rc_min_vbv_use <var>float</var> (<em>encoding,video</em>)</samp></dt>
<dt><samp>ticks_per_frame <var>integer</var> (<em>decoding/encoding,audio,video</em>)</samp></dt>
<dt><samp>color_primaries <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dt><samp>color_trc <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dt><samp>colorspace <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dt><samp>color_range <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dd><p>If used as input parameter, it serves as a hint to the decoder, which
color_range the input has.
</p>
</dd>
<dt><samp>chroma_sample_location <var>integer</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dt><samp>log_level_offset <var>integer</var></samp></dt>
<dd><p>Set the log level offset.
</p>
</dd>
<dt><samp>slices <var>integer</var> (<em>encoding,video</em>)</samp></dt>
<dd><p>Number of slices, used in parallelized encoding.
</p>
</dd>
<dt><samp>thread_type <var>flags</var> (<em>decoding/encoding,video</em>)</samp></dt>
<dd><p>Select which multithreading methods to use.
</p>
<p>Use of &lsquo;<samp>frame</samp>&rsquo; will increase decoding delay by one frame per
thread, so clients which cannot provide future frames should not use
it.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>slice</samp>&rsquo;</dt>
<dd><p>Decode more than one part of a single frame at once.
</p>
<p>Multithreading using slices works only when the video was encoded with
slices.
</p>
</dd>
<dt>&lsquo;<samp>frame</samp>&rsquo;</dt>
<dd><p>Decode more than one frame at once.
</p></dd>
</dl>

<p>Default value is &lsquo;<samp>slice+frame</samp>&rsquo;.
</p>
</dd>
<dt><samp>audio_service_type <var>integer</var> (<em>encoding,audio</em>)</samp></dt>
<dd><p>Set audio service type.
</p>
<p>Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>ma</samp>&rsquo;</dt>
<dd><p>Main Audio Service
</p></dd>
<dt>&lsquo;<samp>ef</samp>&rsquo;</dt>
<dd><p>Effects
</p></dd>
<dt>&lsquo;<samp>vi</samp>&rsquo;</dt>
<dd><p>Visually Impaired
</p></dd>
<dt>&lsquo;<samp>hi</samp>&rsquo;</dt>
<dd><p>Hearing Impaired
</p></dd>
<dt>&lsquo;<samp>di</samp>&rsquo;</dt>
<dd><p>Dialogue
</p></dd>
<dt>&lsquo;<samp>co</samp>&rsquo;</dt>
<dd><p>Commentary
</p></dd>
<dt>&lsquo;<samp>em</samp>&rsquo;</dt>
<dd><p>Emergency
</p></dd>
<dt>&lsquo;<samp>vo</samp>&rsquo;</dt>
<dd><p>Voice Over
</p></dd>
<dt>&lsquo;<samp>ka</samp>&rsquo;</dt>
<dd><p>Karaoke
</p></dd>
</dl>

</dd>
<dt><samp>request_sample_fmt <var>sample_fmt</var> (<em>decoding,audio</em>)</samp></dt>
<dd><p>Set sample format audio decoders should prefer. Default value is
<code>none</code>.
</p>
</dd>
<dt><samp>pkt_timebase <var>rational number</var></samp></dt>
<dt><samp>sub_charenc <var>encoding</var> (<em>decoding,subtitles</em>)</samp></dt>
<dd><p>Set the input subtitles character encoding.
</p>
</dd>
<dt><samp>field_order  <var>field_order</var> (<em>video</em>)</samp></dt>
<dd><p>Set/override the field order of the video.
Possible values:
</p><dl compact="compact">
<dt>&lsquo;<samp>progressive</samp>&rsquo;</dt>
<dd><p>Progressive video
</p></dd>
<dt>&lsquo;<samp>tt</samp>&rsquo;</dt>
<dd><p>Interlaced video, top field coded and displayed first
</p></dd>
<dt>&lsquo;<samp>bb</samp>&rsquo;</dt>
<dd><p>Interlaced video, bottom field coded and displayed first
</p></dd>
<dt>&lsquo;<samp>tb</samp>&rsquo;</dt>
<dd><p>Interlaced video, top coded first, bottom displayed first
</p></dd>
<dt>&lsquo;<samp>bt</samp>&rsquo;</dt>
<dd><p>Interlaced video, bottom coded first, top displayed first
</p></dd>
</dl>

</dd>
<dt><samp>skip_alpha <var>integer</var> (<em>decoding,video</em>)</samp></dt>
<dd><p>Set to 1 to disable processing alpha (transparency). This works like the
&lsquo;<samp>gray</samp>&rsquo; flag in the <samp>flags</samp> option which skips chroma information
instead of alpha. Default is 0.
</p>
</dd>
<dt><samp>codec_whitelist <var>list</var> (<em>input</em>)</samp></dt>
<dd><p>&quot;,&quot; separated List of allowed decoders. By default all are allowed.
</p>
</dd>
<dt><samp>dump_separator <var>string</var> (<em>input</em>)</samp></dt>
<dd><p>Separator used to separate the fields printed on the command line about the
Stream parameters.
For example to separate the fields with newlines and indention:
</p><div class="example">
<pre class="example">ffprobe -dump_separator &quot;
                          &quot;  -i ~/videos/matrixbench_mpeg2.mpg
</pre></div>

</dd>
</dl>


<a name="Decoders"></a>
<h2 class="chapter">3 Decoders<span class="pull-right"><a class="anchor hidden-xs" href="#Decoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Decoders" aria-hidden="true">TOC</a></span></h2>

<p>Decoders are configured elements in FFmpeg which allow the decoding of
multimedia streams.
</p>
<p>When you configure your FFmpeg build, all the supported native decoders
are enabled by default. Decoders requiring an external library must be enabled
manually via the corresponding <code>--enable-lib</code> option. You can list all
available decoders using the configure option <code>--list-decoders</code>.
</p>
<p>You can disable all the decoders with the configure option
<code>--disable-decoders</code> and selectively enable / disable single decoders
with the options <code>--enable-decoder=<var>DECODER</var></code> /
<code>--disable-decoder=<var>DECODER</var></code>.
</p>
<p>The option <code>-decoders</code> of the ff* tools will display the list of
enabled decoders.
</p>

<a name="Video-Decoders"></a>
<h2 class="chapter">4 Video Decoders<span class="pull-right"><a class="anchor hidden-xs" href="#Video-Decoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Video-Decoders" aria-hidden="true">TOC</a></span></h2>

<p>A description of some of the currently available video decoders
follows.
</p>
<a name="hevc"></a>
<h3 class="section">4.1 hevc<span class="pull-right"><a class="anchor hidden-xs" href="#hevc" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-hevc" aria-hidden="true">TOC</a></span></h3>

<p>HEVC / H.265 decoder.
</p>
<p>Note: the <samp>skip_loop_filter</samp> option has effect only at level
<code>all</code>.
</p>
<a name="rawvideo"></a>
<h3 class="section">4.2 rawvideo<span class="pull-right"><a class="anchor hidden-xs" href="#rawvideo" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-rawvideo" aria-hidden="true">TOC</a></span></h3>

<p>Raw video decoder.
</p>
<p>This decoder decodes rawvideo streams.
</p>
<a name="Options"></a>
<h4 class="subsection">4.2.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>top <var>top_field_first</var></samp></dt>
<dd><p>Specify the assumed field type of the input video.
</p><dl compact="compact">
<dt><samp>-1</samp></dt>
<dd><p>the video is assumed to be progressive (default)
</p></dd>
<dt><samp>0</samp></dt>
<dd><p>bottom-field-first is assumed
</p></dd>
<dt><samp>1</samp></dt>
<dd><p>top-field-first is assumed
</p></dd>
</dl>

</dd>
</dl>


<a name="Audio-Decoders"></a>
<h2 class="chapter">5 Audio Decoders<span class="pull-right"><a class="anchor hidden-xs" href="#Audio-Decoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Audio-Decoders" aria-hidden="true">TOC</a></span></h2>

<p>A description of some of the currently available audio decoders
follows.
</p>
<a name="ac3"></a>
<h3 class="section">5.1 ac3<span class="pull-right"><a class="anchor hidden-xs" href="#ac3" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ac3" aria-hidden="true">TOC</a></span></h3>

<p>AC-3 audio decoder.
</p>
<p>This decoder implements part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
</p>
<a name="AC_002d3-Decoder-Options"></a>
<h4 class="subsection">5.1.1 AC-3 Decoder Options<span class="pull-right"><a class="anchor hidden-xs" href="#AC_002d3-Decoder-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-AC_002d3-Decoder-Options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-drc_scale <var>value</var></samp></dt>
<dd><p>Dynamic Range Scale Factor. The factor to apply to dynamic range values
from the AC-3 stream. This factor is applied exponentially.
There are 3 notable scale factor ranges:
</p><dl compact="compact">
<dt><samp>drc_scale == 0</samp></dt>
<dd><p>DRC disabled. Produces full range audio.
</p></dd>
<dt><samp>0 &lt; drc_scale &lt;= 1</samp></dt>
<dd><p>DRC enabled.  Applies a fraction of the stream DRC value.
Audio reproduction is between full range and full compression.
</p></dd>
<dt><samp>drc_scale &gt; 1</samp></dt>
<dd><p>DRC enabled. Applies drc_scale asymmetrically.
Loud sounds are fully compressed.  Soft sounds are enhanced.
</p></dd>
</dl>

</dd>
</dl>

<a name="flac-1"></a>
<h3 class="section">5.2 flac<span class="pull-right"><a class="anchor hidden-xs" href="#flac-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-flac-1" aria-hidden="true">TOC</a></span></h3>

<p>FLAC audio decoder.
</p>
<p>This decoder aims to implement the complete FLAC specification from Xiph.
</p>
<a name="FLAC-Decoder-options"></a>
<h4 class="subsection">5.2.1 FLAC Decoder options<span class="pull-right"><a class="anchor hidden-xs" href="#FLAC-Decoder-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-FLAC-Decoder-options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-use_buggy_lpc</samp></dt>
<dd><p>The lavc FLAC encoder used to produce buggy streams with high lpc values
(like the default value). This option makes it possible to decode such streams
correctly by using lavc&rsquo;s old buggy lpc logic for decoding.
</p>
</dd>
</dl>

<a name="ffwavesynth"></a>
<h3 class="section">5.3 ffwavesynth<span class="pull-right"><a class="anchor hidden-xs" href="#ffwavesynth" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ffwavesynth" aria-hidden="true">TOC</a></span></h3>

<p>Internal wave synthetizer.
</p>
<p>This decoder generates wave patterns according to predefined sequences. Its
use is purely internal and the format of the data it accepts is not publicly
documented.
</p>
<a name="libcelt"></a>
<h3 class="section">5.4 libcelt<span class="pull-right"><a class="anchor hidden-xs" href="#libcelt" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libcelt" aria-hidden="true">TOC</a></span></h3>

<p>libcelt decoder wrapper.
</p>
<p>libcelt allows libavcodec to decode the Xiph CELT ultra-low delay audio codec.
Requires the presence of the libcelt headers and library during configuration.
You need to explicitly configure the build with <code>--enable-libcelt</code>.
</p>
<a name="libgsm"></a>
<h3 class="section">5.5 libgsm<span class="pull-right"><a class="anchor hidden-xs" href="#libgsm" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libgsm" aria-hidden="true">TOC</a></span></h3>

<p>libgsm decoder wrapper.
</p>
<p>libgsm allows libavcodec to decode the GSM full rate audio codec. Requires
the presence of the libgsm headers and library during configuration. You need
to explicitly configure the build with <code>--enable-libgsm</code>.
</p>
<p>This decoder supports both the ordinary GSM and the Microsoft variant.
</p>
<a name="libilbc"></a>
<h3 class="section">5.6 libilbc<span class="pull-right"><a class="anchor hidden-xs" href="#libilbc" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libilbc" aria-hidden="true">TOC</a></span></h3>

<p>libilbc decoder wrapper.
</p>
<p>libilbc allows libavcodec to decode the Internet Low Bitrate Codec (iLBC)
audio codec. Requires the presence of the libilbc headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libilbc</code>.
</p>
<a name="Options-1"></a>
<h4 class="subsection">5.6.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-1" aria-hidden="true">TOC</a></span></h4>

<p>The following option is supported by the libilbc wrapper.
</p>
<dl compact="compact">
<dt><samp>enhance</samp></dt>
<dd>
<p>Enable the enhancement of the decoded audio when set to 1. The default
value is 0 (disabled).
</p>
</dd>
</dl>

<a name="libopencore_002damrnb"></a>
<h3 class="section">5.7 libopencore-amrnb<span class="pull-right"><a class="anchor hidden-xs" href="#libopencore_002damrnb" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopencore_002damrnb" aria-hidden="true">TOC</a></span></h3>

<p>libopencore-amrnb decoder wrapper.
</p>
<p>libopencore-amrnb allows libavcodec to decode the Adaptive Multi-Rate
Narrowband audio codec. Using it requires the presence of the
libopencore-amrnb headers and library during configuration. You need to
explicitly configure the build with <code>--enable-libopencore-amrnb</code>.
</p>
<p>An FFmpeg native decoder for AMR-NB exists, so users can decode AMR-NB
without this library.
</p>
<a name="libopencore_002damrwb"></a>
<h3 class="section">5.8 libopencore-amrwb<span class="pull-right"><a class="anchor hidden-xs" href="#libopencore_002damrwb" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopencore_002damrwb" aria-hidden="true">TOC</a></span></h3>

<p>libopencore-amrwb decoder wrapper.
</p>
<p>libopencore-amrwb allows libavcodec to decode the Adaptive Multi-Rate
Wideband audio codec. Using it requires the presence of the
libopencore-amrwb headers and library during configuration. You need to
explicitly configure the build with <code>--enable-libopencore-amrwb</code>.
</p>
<p>An FFmpeg native decoder for AMR-WB exists, so users can decode AMR-WB
without this library.
</p>
<a name="libopus"></a>
<h3 class="section">5.9 libopus<span class="pull-right"><a class="anchor hidden-xs" href="#libopus" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopus" aria-hidden="true">TOC</a></span></h3>

<p>libopus decoder wrapper.
</p>
<p>libopus allows libavcodec to decode the Opus Interactive Audio Codec.
Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libopus</code>.
</p>
<p>An FFmpeg native decoder for Opus exists, so users can decode Opus
without this library.
</p>

<a name="Subtitles-Decoders"></a>
<h2 class="chapter">6 Subtitles Decoders<span class="pull-right"><a class="anchor hidden-xs" href="#Subtitles-Decoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Subtitles-Decoders" aria-hidden="true">TOC</a></span></h2>

<a name="dvbsub"></a>
<h3 class="section">6.1 dvbsub<span class="pull-right"><a class="anchor hidden-xs" href="#dvbsub" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-dvbsub" aria-hidden="true">TOC</a></span></h3>

<a name="Options-2"></a>
<h4 class="subsection">6.1.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-2" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>compute_clut</samp></dt>
<dd><dl compact="compact">
<dt><samp>-1</samp></dt>
<dd><p>Compute clut if no matching CLUT is in the stream.
</p></dd>
<dt><samp>0</samp></dt>
<dd><p>Never compute CLUT
</p></dd>
<dt><samp>1</samp></dt>
<dd><p>Always compute CLUT and override the one provided in the stream.
</p></dd>
</dl>
</dd>
<dt><samp>dvb_substream</samp></dt>
<dd><p>Selects the dvb substream, or all substreams if -1 which is default.
</p>
</dd>
</dl>

<a name="dvdsub"></a>
<h3 class="section">6.2 dvdsub<span class="pull-right"><a class="anchor hidden-xs" href="#dvdsub" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-dvdsub" aria-hidden="true">TOC</a></span></h3>

<p>This codec decodes the bitmap subtitles used in DVDs; the same subtitles can
also be found in VobSub file pairs and in some Matroska files.
</p>
<a name="Options-3"></a>
<h4 class="subsection">6.2.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-3" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-3" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>palette</samp></dt>
<dd><p>Specify the global palette used by the bitmaps. When stored in VobSub, the
palette is normally specified in the index file; in Matroska, the palette is
stored in the codec extra-data in the same format as in VobSub. In DVDs, the
palette is stored in the IFO file, and therefore not available when reading
from dumped VOB files.
</p>
<p>The format for this option is a string containing 16 24-bits hexadecimal
numbers (without 0x prefix) separated by comas, for example <code>0d00ee,
ee450d, 101010, eaeaea, 0ce60b, ec14ed, ebff0b, 0d617a, 7b7b7b, d1d1d1,
7b2a0e, 0d950c, 0f007b, cf0dec, cfa80c, 7c127b</code>.
</p>
</dd>
<dt><samp>ifo_palette</samp></dt>
<dd><p>Specify the IFO file from which the global palette is obtained.
(experimental)
</p>
</dd>
<dt><samp>forced_subs_only</samp></dt>
<dd><p>Only decode subtitle entries marked as forced. Some titles have forced
and non-forced subtitles in the same track. Setting this flag to <code>1</code>
will only keep the forced subtitles. Default value is <code>0</code>.
</p></dd>
</dl>

<a name="libzvbi_002dteletext"></a>
<h3 class="section">6.3 libzvbi-teletext<span class="pull-right"><a class="anchor hidden-xs" href="#libzvbi_002dteletext" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libzvbi_002dteletext" aria-hidden="true">TOC</a></span></h3>

<p>Libzvbi allows libavcodec to decode DVB teletext pages and DVB teletext
subtitles. Requires the presence of the libzvbi headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libzvbi</code>.
</p>
<a name="Options-4"></a>
<h4 class="subsection">6.3.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-4" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-4" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>txt_page</samp></dt>
<dd><p>List of teletext page numbers to decode. You may use the special * string to
match all pages. Pages that do not match the specified list are dropped.
Default value is *.
</p></dd>
<dt><samp>txt_chop_top</samp></dt>
<dd><p>Discards the top teletext line. Default value is 1.
</p></dd>
<dt><samp>txt_format</samp></dt>
<dd><p>Specifies the format of the decoded subtitles. The teletext decoder is capable
of decoding the teletext pages to bitmaps or to simple text, you should use
&quot;bitmap&quot; for teletext pages, because certain graphics and colors cannot be
expressed in simple text. You might use &quot;text&quot; for teletext based subtitles if
your application can handle simple text based subtitles. Default value is
bitmap.
</p></dd>
<dt><samp>txt_left</samp></dt>
<dd><p>X offset of generated bitmaps, default is 0.
</p></dd>
<dt><samp>txt_top</samp></dt>
<dd><p>Y offset of generated bitmaps, default is 0.
</p></dd>
<dt><samp>txt_chop_spaces</samp></dt>
<dd><p>Chops leading and trailing spaces and removes empty lines from the generated
text. This option is useful for teletext based subtitles where empty spaces may
be present at the start or at the end of the lines or empty lines may be
present between the subtitle lines because of double-sized teletext charactes.
Default value is 1.
</p></dd>
<dt><samp>txt_duration</samp></dt>
<dd><p>Sets the display duration of the decoded teletext pages or subtitles in
miliseconds. Default value is 30000 which is 30 seconds.
</p></dd>
<dt><samp>txt_transparent</samp></dt>
<dd><p>Force transparent background of the generated teletext bitmaps. Default value
is 0 which means an opaque (black) background.
</p></dd>
</dl>

<a name="Encoders"></a>
<h2 class="chapter">7 Encoders<span class="pull-right"><a class="anchor hidden-xs" href="#Encoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Encoders" aria-hidden="true">TOC</a></span></h2>

<p>Encoders are configured elements in FFmpeg which allow the encoding of
multimedia streams.
</p>
<p>When you configure your FFmpeg build, all the supported native encoders
are enabled by default. Encoders requiring an external library must be enabled
manually via the corresponding <code>--enable-lib</code> option. You can list all
available encoders using the configure option <code>--list-encoders</code>.
</p>
<p>You can disable all the encoders with the configure option
<code>--disable-encoders</code> and selectively enable / disable single encoders
with the options <code>--enable-encoder=<var>ENCODER</var></code> /
<code>--disable-encoder=<var>ENCODER</var></code>.
</p>
<p>The option <code>-encoders</code> of the ff* tools will display the list of
enabled encoders.
</p>

<a name="Audio-Encoders"></a>
<h2 class="chapter">8 Audio Encoders<span class="pull-right"><a class="anchor hidden-xs" href="#Audio-Encoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Audio-Encoders" aria-hidden="true">TOC</a></span></h2>

<p>A description of some of the currently available audio encoders
follows.
</p>
<a name="aacenc"></a><a name="aac"></a>
<h3 class="section">8.1 aac<span class="pull-right"><a class="anchor hidden-xs" href="#aac" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-aac" aria-hidden="true">TOC</a></span></h3>

<p>Advanced Audio Coding (AAC) encoder.
</p>
<p>This encoder is an experimental FFmpeg-native AAC encoder. Currently only the
low complexity (AAC-LC) profile is supported. To use this encoder, you must set
<samp>strict</samp> option to &lsquo;<samp>experimental</samp>&rsquo; or lower.
</p>
<p>As this encoder is experimental, unexpected behavior may exist from time to
time. For a more stable AAC encoder, see <a href="#libvo_002daacenc">libvo-aacenc</a>. However, be warned
that it has a worse quality reported by some users.
</p>
<p>See also <a href="#libfdk_002daac_002denc">libfdk_aac</a> and <a href="#libfaac">libfaac</a>.
</p>
<a name="Options-5"></a>
<h4 class="subsection">8.1.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-5" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-5" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set bit rate in bits/s. Setting this automatically activates constant bit rate
(CBR) mode.
</p>
</dd>
<dt><samp>q</samp></dt>
<dd><p>Set quality for variable bit rate (VBR) mode. This option is valid only using
the <code>ffmpeg</code> command-line tool. For library interface users, use
<samp>global_quality</samp>.
</p>
</dd>
<dt><samp>stereo_mode</samp></dt>
<dd><p>Set stereo encoding mode. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>Automatically selected by the encoder.
</p>
</dd>
<dt>&lsquo;<samp>ms_off</samp>&rsquo;</dt>
<dd><p>Disable middle/side encoding. This is the default.
</p>
</dd>
<dt>&lsquo;<samp>ms_force</samp>&rsquo;</dt>
<dd><p>Force middle/side encoding.
</p></dd>
</dl>

</dd>
<dt><samp>aac_coder</samp></dt>
<dd><p>Set AAC encoder coding method. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>faac</samp>&rsquo;</dt>
<dd><p>FAAC-inspired method.
</p>
<p>This method is a simplified reimplementation of the method used in FAAC, which
sets thresholds proportional to the band energies, and then decreases all the
thresholds with quantizer steps to find the appropriate quantization with
distortion below threshold band by band.
</p>
<p>The quality of this method is comparable to the two loop searching method
described below, but somewhat a little better and slower.
</p>
</dd>
<dt>&lsquo;<samp>anmr</samp>&rsquo;</dt>
<dd><p>Average noise to mask ratio (ANMR) trellis-based solution.
</p>
<p>This has a theoretic best quality out of all the coding methods, but at the
cost of the slowest speed.
</p>
</dd>
<dt>&lsquo;<samp>twoloop</samp>&rsquo;</dt>
<dd><p>Two loop searching (TLS) method.
</p>
<p>This method first sets quantizers depending on band thresholds and then tries
to find an optimal combination by adding or subtracting a specific value from
all quantizers and adjusting some individual quantizer a little.
</p>
<p>This method produces similar quality with the FAAC method and is the default.
</p>
</dd>
<dt>&lsquo;<samp>fast</samp>&rsquo;</dt>
<dd><p>Constant quantizer method.
</p>
<p>This method sets a constant quantizer for all bands. This is the fastest of all
the methods, yet produces the worst quality.
</p>
</dd>
</dl>

</dd>
</dl>

<a name="ac3-and-ac3_005ffixed"></a>
<h3 class="section">8.2 ac3 and ac3_fixed<span class="pull-right"><a class="anchor hidden-xs" href="#ac3-and-ac3_005ffixed" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ac3-and-ac3_005ffixed" aria-hidden="true">TOC</a></span></h3>

<p>AC-3 audio encoders.
</p>
<p>These encoders implement part of ATSC A/52:2010 and ETSI TS 102 366, as well as
the undocumented RealAudio 3 (a.k.a. dnet).
</p>
<p>The <var>ac3</var> encoder uses floating-point math, while the <var>ac3_fixed</var>
encoder only uses fixed-point integer math. This does not mean that one is
always faster, just that one or the other may be better suited to a
particular system. The floating-point encoder will generally produce better
quality audio for a given bitrate. The <var>ac3_fixed</var> encoder is not the
default codec for any of the output formats, so it must be specified explicitly
using the option <code>-acodec ac3_fixed</code> in order to use it.
</p>
<a name="AC_002d3-Metadata"></a>
<h4 class="subsection">8.2.1 AC-3 Metadata<span class="pull-right"><a class="anchor hidden-xs" href="#AC_002d3-Metadata" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-AC_002d3-Metadata" aria-hidden="true">TOC</a></span></h4>

<p>The AC-3 metadata options are used to set parameters that describe the audio,
but in most cases do not affect the audio encoding itself. Some of the options
do directly affect or influence the decoding and playback of the resulting
bitstream, while others are just for informational purposes. A few of the
options will add bits to the output stream that could otherwise be used for
audio data, and will thus affect the quality of the output. Those will be
indicated accordingly with a note in the option list below.
</p>
<p>These parameters are described in detail in several publicly-available
documents.
</p><ul>
<li> <a href="http://www.atsc.org/cms/standards/a_52-2010.pdf">A/52:2010 - Digital Audio Compression (AC-3) (E-AC-3) Standard</a>
</li><li> <a href="http://www.atsc.org/cms/standards/a_54a_with_corr_1.pdf">A/54 - Guide to the Use of the ATSC Digital Television Standard</a>
</li><li> <a href="http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/18_Metadata.Guide.pdf">Dolby Metadata Guide</a>
</li><li> <a href="http://www.dolby.com/uploadedFiles/zz-_Shared_Assets/English_PDFs/Professional/46_DDEncodingGuidelines.pdf">Dolby Digital Professional Encoding Guidelines</a>
</li></ul>

<a name="Metadata-Control-Options"></a>
<h4 class="subsubsection">8.2.1.1 Metadata Control Options<span class="pull-right"><a class="anchor hidden-xs" href="#Metadata-Control-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Metadata-Control-Options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-per_frame_metadata <var>boolean</var></samp></dt>
<dd><p>Allow Per-Frame Metadata. Specifies if the encoder should check for changing
metadata for each frame.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dd><p>The metadata values set at initialization will be used for every frame in the
stream. (default)
</p></dd>
<dt><samp>1</samp></dt>
<dd><p>Metadata values can be changed before encoding each frame.
</p></dd>
</dl>

</dd>
</dl>

<a name="Downmix-Levels"></a>
<h4 class="subsubsection">8.2.1.2 Downmix Levels<span class="pull-right"><a class="anchor hidden-xs" href="#Downmix-Levels" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Downmix-Levels" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-center_mixlev <var>level</var></samp></dt>
<dd><p>Center Mix Level. The amount of gain the decoder should apply to the center
channel when downmixing to stereo. This field will only be written to the
bitstream if a center channel is present. The value is specified as a scale
factor. There are 3 valid values:
</p><dl compact="compact">
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3dB gain
</p></dd>
<dt><samp>0.595</samp></dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6dB gain
</p></dd>
</dl>

</dd>
<dt><samp>-surround_mixlev <var>level</var></samp></dt>
<dd><p>Surround Mix Level. The amount of gain the decoder should apply to the surround
channel(s) when downmixing to stereo. This field will only be written to the
bitstream if one or more surround channels are present. The value is specified
as a scale factor.  There are 3 valid values:
</p><dl compact="compact">
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3dB gain
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6dB gain (default)
</p></dd>
<dt><samp>0.000</samp></dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>

</dd>
</dl>

<a name="Audio-Production-Information"></a>
<h4 class="subsubsection">8.2.1.3 Audio Production Information<span class="pull-right"><a class="anchor hidden-xs" href="#Audio-Production-Information" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Audio-Production-Information" aria-hidden="true">TOC</a></span></h4>
<p>Audio Production Information is optional information describing the mixing
environment.  Either none or both of the fields are written to the bitstream.
</p>
<dl compact="compact">
<dt><samp>-mixing_level <var>number</var></samp></dt>
<dd><p>Mixing Level. Specifies peak sound pressure level (SPL) in the production
environment when the mix was mastered. Valid values are 80 to 111, or -1 for
unknown or not indicated. The default value is -1, but that value cannot be
used if the Audio Production Information is written to the bitstream. Therefore,
if the <code>room_type</code> option is not the default value, the <code>mixing_level</code>
option must not be -1.
</p>
</dd>
<dt><samp>-room_type <var>type</var></samp></dt>
<dd><p>Room Type. Describes the equalization used during the final mixing session at
the studio or on the dubbing stage. A large room is a dubbing stage with the
industry standard X-curve equalization; a small room has flat equalization.
This field will not be written to the bitstream if both the <code>mixing_level</code>
option and the <code>room_type</code> option have the default values.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>notindicated</samp></dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>large</samp></dt>
<dd><p>Large Room
</p></dd>
<dt><samp>2</samp></dt>
<dt><samp>small</samp></dt>
<dd><p>Small Room
</p></dd>
</dl>

</dd>
</dl>

<a name="Other-Metadata-Options"></a>
<h4 class="subsubsection">8.2.1.4 Other Metadata Options<span class="pull-right"><a class="anchor hidden-xs" href="#Other-Metadata-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Other-Metadata-Options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-copyright <var>boolean</var></samp></dt>
<dd><p>Copyright Indicator. Specifies whether a copyright exists for this audio.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>No Copyright Exists (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Copyright Exists
</p></dd>
</dl>

</dd>
<dt><samp>-dialnorm <var>value</var></samp></dt>
<dd><p>Dialogue Normalization. Indicates how far the average dialogue level of the
program is below digital 100% full scale (0 dBFS). This parameter determines a
level shift during audio reproduction that sets the average volume of the
dialogue to a preset level. The goal is to match volume level between program
sources. A value of -31dB will result in no volume level change, relative to
the source volume, during audio reproduction. Valid values are whole numbers in
the range -31 to -1, with -31 being the default.
</p>
</dd>
<dt><samp>-dsur_mode <var>mode</var></samp></dt>
<dd><p>Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround
(Pro Logic). This field will only be written to the bitstream if the audio
stream is stereo. Using this option does <b>NOT</b> mean the encoder will actually
apply Dolby Surround processing.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>notindicated</samp></dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>Not Dolby Surround Encoded
</p></dd>
<dt><samp>2</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Dolby Surround Encoded
</p></dd>
</dl>

</dd>
<dt><samp>-original <var>boolean</var></samp></dt>
<dd><p>Original Bit Stream Indicator. Specifies whether this audio is from the
original source and not a copy.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>Not Original Source
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Original Source (default)
</p></dd>
</dl>

</dd>
</dl>

<a name="Extended-Bitstream-Information"></a>
<h4 class="subsection">8.2.2 Extended Bitstream Information<span class="pull-right"><a class="anchor hidden-xs" href="#Extended-Bitstream-Information" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Extended-Bitstream-Information" aria-hidden="true">TOC</a></span></h4>
<p>The extended bitstream options are part of the Alternate Bit Stream Syntax as
specified in Annex D of the A/52:2010 standard. It is grouped into 2 parts.
If any one parameter in a group is specified, all values in that group will be
written to the bitstream.  Default values are used for those that are written
but have not been specified.  If the mixing levels are written, the decoder
will use these values instead of the ones specified in the <code>center_mixlev</code>
and <code>surround_mixlev</code> options if it supports the Alternate Bit Stream
Syntax.
</p>
<a name="Extended-Bitstream-Information-_002d-Part-1"></a>
<h4 class="subsubsection">8.2.2.1 Extended Bitstream Information - Part 1<span class="pull-right"><a class="anchor hidden-xs" href="#Extended-Bitstream-Information-_002d-Part-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Extended-Bitstream-Information-_002d-Part-1" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-dmix_mode <var>mode</var></samp></dt>
<dd><p>Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt
(Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>notindicated</samp></dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>ltrt</samp></dt>
<dd><p>Lt/Rt Downmix Preferred
</p></dd>
<dt><samp>2</samp></dt>
<dt><samp>loro</samp></dt>
<dd><p>Lo/Ro Downmix Preferred
</p></dd>
</dl>

</dd>
<dt><samp>-ltrt_cmixlev <var>level</var></samp></dt>
<dd><p>Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the
center channel when downmixing to stereo in Lt/Rt mode.
</p><dl compact="compact">
<dt><samp>1.414</samp></dt>
<dd><p>Apply +3dB gain
</p></dd>
<dt><samp>1.189</samp></dt>
<dd><p>Apply +1.5dB gain
</p></dd>
<dt><samp>1.000</samp></dt>
<dd><p>Apply 0dB gain
</p></dd>
<dt><samp>0.841</samp></dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt><samp>0.595</samp></dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6.0dB gain
</p></dd>
<dt><samp>0.000</samp></dt>
<dd><p>Silence Center Channel
</p></dd>
</dl>

</dd>
<dt><samp>-ltrt_surmixlev <var>level</var></samp></dt>
<dd><p>Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the
surround channel(s) when downmixing to stereo in Lt/Rt mode.
</p><dl compact="compact">
<dt><samp>0.841</samp></dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt><samp>0.595</samp></dt>
<dd><p>Apply -4.5dB gain
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6.0dB gain (default)
</p></dd>
<dt><samp>0.000</samp></dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>

</dd>
<dt><samp>-loro_cmixlev <var>level</var></samp></dt>
<dd><p>Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the
center channel when downmixing to stereo in Lo/Ro mode.
</p><dl compact="compact">
<dt><samp>1.414</samp></dt>
<dd><p>Apply +3dB gain
</p></dd>
<dt><samp>1.189</samp></dt>
<dd><p>Apply +1.5dB gain
</p></dd>
<dt><samp>1.000</samp></dt>
<dd><p>Apply 0dB gain
</p></dd>
<dt><samp>0.841</samp></dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt><samp>0.595</samp></dt>
<dd><p>Apply -4.5dB gain (default)
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6.0dB gain
</p></dd>
<dt><samp>0.000</samp></dt>
<dd><p>Silence Center Channel
</p></dd>
</dl>

</dd>
<dt><samp>-loro_surmixlev <var>level</var></samp></dt>
<dd><p>Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the
surround channel(s) when downmixing to stereo in Lo/Ro mode.
</p><dl compact="compact">
<dt><samp>0.841</samp></dt>
<dd><p>Apply -1.5dB gain
</p></dd>
<dt><samp>0.707</samp></dt>
<dd><p>Apply -3.0dB gain
</p></dd>
<dt><samp>0.595</samp></dt>
<dd><p>Apply -4.5dB gain
</p></dd>
<dt><samp>0.500</samp></dt>
<dd><p>Apply -6.0dB gain (default)
</p></dd>
<dt><samp>0.000</samp></dt>
<dd><p>Silence Surround Channel(s)
</p></dd>
</dl>

</dd>
</dl>

<a name="Extended-Bitstream-Information-_002d-Part-2"></a>
<h4 class="subsubsection">8.2.2.2 Extended Bitstream Information - Part 2<span class="pull-right"><a class="anchor hidden-xs" href="#Extended-Bitstream-Information-_002d-Part-2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Extended-Bitstream-Information-_002d-Part-2" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-dsurex_mode <var>mode</var></samp></dt>
<dd><p>Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX
(7.1 matrixed to 5.1). Using this option does <b>NOT</b> mean the encoder will actually
apply Dolby Surround EX processing.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>notindicated</samp></dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Dolby Surround EX Off
</p></dd>
<dt><samp>2</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>Dolby Surround EX On
</p></dd>
</dl>

</dd>
<dt><samp>-dheadphone_mode <var>mode</var></samp></dt>
<dd><p>Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone
encoding (multi-channel matrixed to 2.0 for use with headphones). Using this
option does <b>NOT</b> mean the encoder will actually apply Dolby Headphone
processing.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>notindicated</samp></dt>
<dd><p>Not Indicated (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Dolby Headphone Off
</p></dd>
<dt><samp>2</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>Dolby Headphone On
</p></dd>
</dl>

</dd>
<dt><samp>-ad_conv_type <var>type</var></samp></dt>
<dd><p>A/D Converter Type. Indicates whether the audio has passed through HDCD A/D
conversion.
</p><dl compact="compact">
<dt><samp>0</samp></dt>
<dt><samp>standard</samp></dt>
<dd><p>Standard A/D Converter (default)
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>hdcd</samp></dt>
<dd><p>HDCD A/D Converter
</p></dd>
</dl>

</dd>
</dl>

<a name="Other-AC_002d3-Encoding-Options"></a>
<h4 class="subsection">8.2.3 Other AC-3 Encoding Options<span class="pull-right"><a class="anchor hidden-xs" href="#Other-AC_002d3-Encoding-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Other-AC_002d3-Encoding-Options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-stereo_rematrixing <var>boolean</var></samp></dt>
<dd><p>Stereo Rematrixing. Enables/Disables use of rematrixing for stereo input. This
is an optional AC-3 feature that increases quality by selectively encoding
the left/right channels as mid/side. This option is enabled by default, and it
is highly recommended that it be left as enabled except for testing purposes.
</p>
</dd>
</dl>

<a name="Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options"></a>
<h4 class="subsection">8.2.4 Floating-Point-Only AC-3 Encoding Options<span class="pull-right"><a class="anchor hidden-xs" href="#Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Floating_002dPoint_002dOnly-AC_002d3-Encoding-Options" aria-hidden="true">TOC</a></span></h4>

<p>These options are only valid for the floating-point encoder and do not exist
for the fixed-point encoder due to the corresponding features not being
implemented in fixed-point.
</p>
<dl compact="compact">
<dt><samp>-channel_coupling <var>boolean</var></samp></dt>
<dd><p>Enables/Disables use of channel coupling, which is an optional AC-3 feature
that increases quality by combining high frequency information from multiple
channels into a single channel. The per-channel high frequency information is
sent with less accuracy in both the frequency and time domains. This allows
more bits to be used for lower frequencies while preserving enough information
to reconstruct the high frequencies. This option is enabled by default for the
floating-point encoder and should generally be left as enabled except for
testing purposes or to increase encoding speed.
</p><dl compact="compact">
<dt><samp>-1</samp></dt>
<dt><samp>auto</samp></dt>
<dd><p>Selected by Encoder (default)
</p></dd>
<dt><samp>0</samp></dt>
<dt><samp>off</samp></dt>
<dd><p>Disable Channel Coupling
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>on</samp></dt>
<dd><p>Enable Channel Coupling
</p></dd>
</dl>

</dd>
<dt><samp>-cpl_start_band <var>number</var></samp></dt>
<dd><p>Coupling Start Band. Sets the channel coupling start band, from 1 to 15. If a
value higher than the bandwidth is used, it will be reduced to 1 less than the
coupling end band. If <var>auto</var> is used, the start band will be determined by
the encoder based on the bit rate, sample rate, and channel layout. This option
has no effect if channel coupling is disabled.
</p><dl compact="compact">
<dt><samp>-1</samp></dt>
<dt><samp>auto</samp></dt>
<dd><p>Selected by Encoder (default)
</p></dd>
</dl>

</dd>
</dl>

<a name="flac"></a><a name="flac-2"></a>
<h3 class="section">8.3 flac<span class="pull-right"><a class="anchor hidden-xs" href="#flac-2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-flac-2" aria-hidden="true">TOC</a></span></h3>

<p>FLAC (Free Lossless Audio Codec) Encoder
</p>
<a name="Options-6"></a>
<h4 class="subsection">8.3.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-6" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-6" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by FFmpeg&rsquo;s flac encoder.
</p>
<dl compact="compact">
<dt><samp>compression_level</samp></dt>
<dd><p>Sets the compression level, which chooses defaults for many other options
if they are not set explicitly.
</p>
</dd>
<dt><samp>frame_size</samp></dt>
<dd><p>Sets the size of the frames in samples per channel.
</p>
</dd>
<dt><samp>lpc_coeff_precision</samp></dt>
<dd><p>Sets the LPC coefficient precision, valid values are from 1 to 15, 15 is the
default.
</p>
</dd>
<dt><samp>lpc_type</samp></dt>
<dd><p>Sets the first stage LPC algorithm
</p><dl compact="compact">
<dt>&lsquo;<samp>none</samp>&rsquo;</dt>
<dd><p>LPC is not used
</p>
</dd>
<dt>&lsquo;<samp>fixed</samp>&rsquo;</dt>
<dd><p>fixed LPC coefficients
</p>
</dd>
<dt>&lsquo;<samp>levinson</samp>&rsquo;</dt>
<dt>&lsquo;<samp>cholesky</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>lpc_passes</samp></dt>
<dd><p>Number of passes to use for Cholesky factorization during LPC analysis
</p>
</dd>
<dt><samp>min_partition_order</samp></dt>
<dd><p>The minimum partition order
</p>
</dd>
<dt><samp>max_partition_order</samp></dt>
<dd><p>The maximum partition order
</p>
</dd>
<dt><samp>prediction_order_method</samp></dt>
<dd><dl compact="compact">
<dt>&lsquo;<samp>estimation</samp>&rsquo;</dt>
<dt>&lsquo;<samp>2level</samp>&rsquo;</dt>
<dt>&lsquo;<samp>4level</samp>&rsquo;</dt>
<dt>&lsquo;<samp>8level</samp>&rsquo;</dt>
<dt>&lsquo;<samp>search</samp>&rsquo;</dt>
<dd><p>Bruteforce search
</p></dd>
<dt>&lsquo;<samp>log</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>ch_mode</samp></dt>
<dd><p>Channel mode
</p><dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>The mode is chosen automatically for each frame
</p></dd>
<dt>&lsquo;<samp>indep</samp>&rsquo;</dt>
<dd><p>Chanels are independently coded
</p></dd>
<dt>&lsquo;<samp>left_side</samp>&rsquo;</dt>
<dt>&lsquo;<samp>right_side</samp>&rsquo;</dt>
<dt>&lsquo;<samp>mid_side</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>exact_rice_parameters</samp></dt>
<dd><p>Chooses if rice parameters are calculated exactly or approximately.
if set to 1 then they are chosen exactly, which slows the code down slightly and
improves compression slightly.
</p>
</dd>
<dt><samp>multi_dim_quant</samp></dt>
<dd><p>Multi Dimensional Quantization. If set to 1 then a 2nd stage LPC algorithm is
applied after the first stage to finetune the coefficients. This is quite slow
and slightly improves compression.
</p>
</dd>
</dl>

<a name="libfaac"></a><a name="libfaac-1"></a>
<h3 class="section">8.4 libfaac<span class="pull-right"><a class="anchor hidden-xs" href="#libfaac-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libfaac-1" aria-hidden="true">TOC</a></span></h3>

<p>libfaac AAC (Advanced Audio Coding) encoder wrapper.
</p>
<p>Requires the presence of the libfaac headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libfaac --enable-nonfree</code>.
</p>
<p>This encoder is considered to be of higher quality with respect to the
<a href="#aacenc">the native experimental FFmpeg AAC encoder</a>.
</p>
<p>For more information see the libfaac project at
<a href="http://www.audiocoding.com/faac.html/">http://www.audiocoding.com/faac.html/</a>.
</p>
<a name="Options-7"></a>
<h4 class="subsection">8.4.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-7" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-7" aria-hidden="true">TOC</a></span></h4>

<p>The following shared FFmpeg codec options are recognized.
</p>
<p>The following options are supported by the libfaac wrapper. The
<code>faac</code>-equivalent of the options are listed in parentheses.
</p>
<dl compact="compact">
<dt><samp>b (<em>-b</em>)</samp></dt>
<dd><p>Set bit rate in bits/s for ABR (Average Bit Rate) mode. If the bit rate
is not explicitly specified, it is automatically set to a suitable
value depending on the selected profile. <code>faac</code> bitrate is
expressed in kilobits/s.
</p>
<p>Note that libfaac does not support CBR (Constant Bit Rate) but only
ABR (Average Bit Rate).
</p>
<p>If VBR mode is enabled this option is ignored.
</p>
</dd>
<dt><samp>ar (<em>-R</em>)</samp></dt>
<dd><p>Set audio sampling rate (in Hz).
</p>
</dd>
<dt><samp>ac (<em>-c</em>)</samp></dt>
<dd><p>Set the number of audio channels.
</p>
</dd>
<dt><samp>cutoff (<em>-C</em>)</samp></dt>
<dd><p>Set cutoff frequency. If not specified (or explicitly set to 0) it
will use a value automatically computed by the library. Default value
is 0.
</p>
</dd>
<dt><samp>profile</samp></dt>
<dd><p>Set audio profile.
</p>
<p>The following profiles are recognized:
</p><dl compact="compact">
<dt>&lsquo;<samp>aac_main</samp>&rsquo;</dt>
<dd><p>Main AAC (Main)
</p>
</dd>
<dt>&lsquo;<samp>aac_low</samp>&rsquo;</dt>
<dd><p>Low Complexity AAC (LC)
</p>
</dd>
<dt>&lsquo;<samp>aac_ssr</samp>&rsquo;</dt>
<dd><p>Scalable Sample Rate (SSR)
</p>
</dd>
<dt>&lsquo;<samp>aac_ltp</samp>&rsquo;</dt>
<dd><p>Long Term Prediction (LTP)
</p></dd>
</dl>

<p>If not specified it is set to &lsquo;<samp>aac_low</samp>&rsquo;.
</p>
</dd>
<dt><samp>flags +qscale</samp></dt>
<dd><p>Set constant quality VBR (Variable Bit Rate) mode.
</p>
</dd>
<dt><samp>global_quality</samp></dt>
<dd><p>Set quality in VBR mode as an integer number of lambda units.
</p>
<p>Only relevant when VBR mode is enabled with <code>flags +qscale</code>.  The
value is converted to QP units by dividing it by <code>FF_QP2LAMBDA</code>,
and used to set the quality value used by libfaac. A reasonable range
for the option value in QP units is [10-500], the higher the value the
higher the quality.
</p>
</dd>
<dt><samp>q (<em>-q</em>)</samp></dt>
<dd><p>Enable VBR mode when set to a non-negative value, and set constant
quality value as a double floating point value in QP units.
</p>
<p>The value sets the quality value used by libfaac. A reasonable range
for the option value is [10-500], the higher the value the higher the
quality.
</p>
<p>This option is valid only using the <code>ffmpeg</code> command-line
tool. For library interface users, use <samp>global_quality</samp>.
</p></dd>
</dl>

<a name="Examples"></a>
<h4 class="subsection">8.4.2 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples" aria-hidden="true">TOC</a></span></h4>

<ul>
<li> Use <code>ffmpeg</code> to convert an audio file to ABR 128 kbps AAC in an M4A (MP4)
container:
<div class="example">
<pre class="example">ffmpeg -i input.wav -codec:a libfaac -b:a 128k -output.m4a
</pre></div>

</li><li> Use <code>ffmpeg</code> to convert an audio file to VBR AAC, using the
LTP AAC profile:
<div class="example">
<pre class="example">ffmpeg -i input.wav -c:a libfaac -profile:a aac_ltp -q:a 100 output.m4a
</pre></div>
</li></ul>

<a name="libfdk_002daac_002denc"></a><a name="libfdk_005faac"></a>
<h3 class="section">8.5 libfdk_aac<span class="pull-right"><a class="anchor hidden-xs" href="#libfdk_005faac" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libfdk_005faac" aria-hidden="true">TOC</a></span></h3>

<p>libfdk-aac AAC (Advanced Audio Coding) encoder wrapper.
</p>
<p>The libfdk-aac library is based on the Fraunhofer FDK AAC code from
the Android project.
</p>
<p>Requires the presence of the libfdk-aac headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libfdk-aac</code>. The library is also incompatible with GPL,
so if you allow the use of GPL, you should configure with
<code>--enable-gpl --enable-nonfree --enable-libfdk-aac</code>.
</p>
<p>This encoder is considered to be of higher quality with respect to
both <a href="#aacenc">the native experimental FFmpeg AAC encoder</a> and
<a href="#libfaac">libfaac</a>.
</p>
<p>VBR encoding, enabled through the <samp>vbr</samp> or <samp>flags
+qscale</samp> options, is experimental and only works with some
combinations of parameters.
</p>
<p>Support for encoding 7.1 audio is only available with libfdk-aac 0.1.3 or
higher.
</p>
<p>For more information see the fdk-aac project at
<a href="http://sourceforge.net/p/opencore-amr/fdk-aac/">http://sourceforge.net/p/opencore-amr/fdk-aac/</a>.
</p>
<a name="Options-8"></a>
<h4 class="subsection">8.5.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-8" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-8" aria-hidden="true">TOC</a></span></h4>

<p>The following options are mapped on the shared FFmpeg codec options.
</p>
<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set bit rate in bits/s. If the bitrate is not explicitly specified, it
is automatically set to a suitable value depending on the selected
profile.
</p>
<p>In case VBR mode is enabled the option is ignored.
</p>
</dd>
<dt><samp>ar</samp></dt>
<dd><p>Set audio sampling rate (in Hz).
</p>
</dd>
<dt><samp>channels</samp></dt>
<dd><p>Set the number of audio channels.
</p>
</dd>
<dt><samp>flags +qscale</samp></dt>
<dd><p>Enable fixed quality, VBR (Variable Bit Rate) mode.
Note that VBR is implicitly enabled when the <samp>vbr</samp> value is
positive.
</p>
</dd>
<dt><samp>cutoff</samp></dt>
<dd><p>Set cutoff frequency. If not specified (or explicitly set to 0) it
will use a value automatically computed by the library. Default value
is 0.
</p>
</dd>
<dt><samp>profile</samp></dt>
<dd><p>Set audio profile.
</p>
<p>The following profiles are recognized:
</p><dl compact="compact">
<dt>&lsquo;<samp>aac_low</samp>&rsquo;</dt>
<dd><p>Low Complexity AAC (LC)
</p>
</dd>
<dt>&lsquo;<samp>aac_he</samp>&rsquo;</dt>
<dd><p>High Efficiency AAC (HE-AAC)
</p>
</dd>
<dt>&lsquo;<samp>aac_he_v2</samp>&rsquo;</dt>
<dd><p>High Efficiency AAC version 2 (HE-AACv2)
</p>
</dd>
<dt>&lsquo;<samp>aac_ld</samp>&rsquo;</dt>
<dd><p>Low Delay AAC (LD)
</p>
</dd>
<dt>&lsquo;<samp>aac_eld</samp>&rsquo;</dt>
<dd><p>Enhanced Low Delay AAC (ELD)
</p></dd>
</dl>

<p>If not specified it is set to &lsquo;<samp>aac_low</samp>&rsquo;.
</p></dd>
</dl>

<p>The following are private options of the libfdk_aac encoder.
</p>
<dl compact="compact">
<dt><samp>afterburner</samp></dt>
<dd><p>Enable afterburner feature if set to 1, disabled if set to 0. This
improves the quality but also the required processing power.
</p>
<p>Default value is 1.
</p>
</dd>
<dt><samp>eld_sbr</samp></dt>
<dd><p>Enable SBR (Spectral Band Replication) for ELD if set to 1, disabled
if set to 0.
</p>
<p>Default value is 0.
</p>
</dd>
<dt><samp>signaling</samp></dt>
<dd><p>Set SBR/PS signaling style.
</p>
<p>It can assume one of the following values:
</p><dl compact="compact">
<dt>&lsquo;<samp>default</samp>&rsquo;</dt>
<dd><p>choose signaling implicitly (explicit hierarchical by default,
implicit if global header is disabled)
</p>
</dd>
<dt>&lsquo;<samp>implicit</samp>&rsquo;</dt>
<dd><p>implicit backwards compatible signaling
</p>
</dd>
<dt>&lsquo;<samp>explicit_sbr</samp>&rsquo;</dt>
<dd><p>explicit SBR, implicit PS signaling
</p>
</dd>
<dt>&lsquo;<samp>explicit_hierarchical</samp>&rsquo;</dt>
<dd><p>explicit hierarchical signaling
</p></dd>
</dl>

<p>Default value is &lsquo;<samp>default</samp>&rsquo;.
</p>
</dd>
<dt><samp>latm</samp></dt>
<dd><p>Output LATM/LOAS encapsulated data if set to 1, disabled if set to 0.
</p>
<p>Default value is 0.
</p>
</dd>
<dt><samp>header_period</samp></dt>
<dd><p>Set StreamMuxConfig and PCE repetition period (in frames) for sending
in-band configuration buffers within LATM/LOAS transport layer.
</p>
<p>Must be a 16-bits non-negative integer.
</p>
<p>Default value is 0.
</p>
</dd>
<dt><samp>vbr</samp></dt>
<dd><p>Set VBR mode, from 1 to 5. 1 is lowest quality (though still pretty
good) and 5 is highest quality. A value of 0 will disable VBR, and CBR
(Constant Bit Rate) is enabled.
</p>
<p>Currently only the &lsquo;<samp>aac_low</samp>&rsquo; profile supports VBR encoding.
</p>
<p>VBR modes 1-5 correspond to roughly the following average bit rates:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>1</samp>&rsquo;</dt>
<dd><p>32 kbps/channel
</p></dd>
<dt>&lsquo;<samp>2</samp>&rsquo;</dt>
<dd><p>40 kbps/channel
</p></dd>
<dt>&lsquo;<samp>3</samp>&rsquo;</dt>
<dd><p>48-56 kbps/channel
</p></dd>
<dt>&lsquo;<samp>4</samp>&rsquo;</dt>
<dd><p>64 kbps/channel
</p></dd>
<dt>&lsquo;<samp>5</samp>&rsquo;</dt>
<dd><p>about 80-96 kbps/channel
</p></dd>
</dl>

<p>Default value is 0.
</p></dd>
</dl>

<a name="Examples-1"></a>
<h4 class="subsection">8.5.2 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples-1" aria-hidden="true">TOC</a></span></h4>

<ul>
<li> Use <code>ffmpeg</code> to convert an audio file to VBR AAC in an M4A (MP4)
container:
<div class="example">
<pre class="example">ffmpeg -i input.wav -codec:a libfdk_aac -vbr 3 output.m4a
</pre></div>

</li><li> Use <code>ffmpeg</code> to convert an audio file to CBR 64k kbps AAC, using the
High-Efficiency AAC profile:
<div class="example">
<pre class="example">ffmpeg -i input.wav -c:a libfdk_aac -profile:a aac_he -b:a 64k output.m4a
</pre></div>
</li></ul>

<a name="libmp3lame"></a><a name="libmp3lame-1"></a>
<h3 class="section">8.6 libmp3lame<span class="pull-right"><a class="anchor hidden-xs" href="#libmp3lame-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libmp3lame-1" aria-hidden="true">TOC</a></span></h3>

<p>LAME (Lame Ain&rsquo;t an MP3 Encoder) MP3 encoder wrapper.
</p>
<p>Requires the presence of the libmp3lame headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libmp3lame</code>.
</p>
<p>See <a href="#libshine">libshine</a> for a fixed-point MP3 encoder, although with a
lower quality.
</p>
<a name="Options-9"></a>
<h4 class="subsection">8.6.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-9" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-9" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libmp3lame wrapper. The
<code>lame</code>-equivalent of the options are listed in parentheses.
</p>
<dl compact="compact">
<dt><samp>b (<em>-b</em>)</samp></dt>
<dd><p>Set bitrate expressed in bits/s for CBR or ABR. LAME <code>bitrate</code> is
expressed in kilobits/s.
</p>
</dd>
<dt><samp>q (<em>-V</em>)</samp></dt>
<dd><p>Set constant quality setting for VBR. This option is valid only
using the <code>ffmpeg</code> command-line tool. For library interface
users, use <samp>global_quality</samp>.
</p>
</dd>
<dt><samp>compression_level (<em>-q</em>)</samp></dt>
<dd><p>Set algorithm quality. Valid arguments are integers in the 0-9 range,
with 0 meaning highest quality but slowest, and 9 meaning fastest
while producing the worst quality.
</p>
</dd>
<dt><samp>reservoir</samp></dt>
<dd><p>Enable use of bit reservoir when set to 1. Default value is 1. LAME
has this enabled by default, but can be overridden by use
<samp>--nores</samp> option.
</p>
</dd>
<dt><samp>joint_stereo (<em>-m j</em>)</samp></dt>
<dd><p>Enable the encoder to use (on a frame by frame basis) either L/R
stereo or mid/side stereo. Default value is 1.
</p>
</dd>
<dt><samp>abr (<em>--abr</em>)</samp></dt>
<dd><p>Enable the encoder to use ABR when set to 1. The <code>lame</code>
<samp>--abr</samp> sets the target bitrate, while this options only
tells FFmpeg to use ABR still relies on <samp>b</samp> to set bitrate.
</p>
</dd>
</dl>

<a name="libopencore_002damrnb-1"></a>
<h3 class="section">8.7 libopencore-amrnb<span class="pull-right"><a class="anchor hidden-xs" href="#libopencore_002damrnb-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopencore_002damrnb-1" aria-hidden="true">TOC</a></span></h3>

<p>OpenCORE Adaptive Multi-Rate Narrowband encoder.
</p>
<p>Requires the presence of the libopencore-amrnb headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libopencore-amrnb --enable-version3</code>.
</p>
<p>This is a mono-only encoder. Officially it only supports 8000Hz sample rate,
but you can override it by setting <samp>strict</samp> to &lsquo;<samp>unofficial</samp>&rsquo; or
lower.
</p>
<a name="Options-10"></a>
<h4 class="subsection">8.7.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-10" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-10" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set bitrate in bits per second. Only the following bitrates are supported,
otherwise libavcodec will round to the nearest valid bitrate.
</p>
<dl compact="compact">
<dt><samp>4750</samp></dt>
<dt><samp>5150</samp></dt>
<dt><samp>5900</samp></dt>
<dt><samp>6700</samp></dt>
<dt><samp>7400</samp></dt>
<dt><samp>7950</samp></dt>
<dt><samp>10200</samp></dt>
<dt><samp>12200</samp></dt>
</dl>

</dd>
<dt><samp>dtx</samp></dt>
<dd><p>Allow discontinuous transmission (generate comfort noise) when set to 1. The
default value is 0 (disabled).
</p>
</dd>
</dl>

<a name="libshine"></a><a name="libshine-1"></a>
<h3 class="section">8.8 libshine<span class="pull-right"><a class="anchor hidden-xs" href="#libshine-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libshine-1" aria-hidden="true">TOC</a></span></h3>

<p>Shine Fixed-Point MP3 encoder wrapper.
</p>
<p>Shine is a fixed-point MP3 encoder. It has a far better performance on
platforms without an FPU, e.g. armel CPUs, and some phones and tablets.
However, as it is more targeted on performance than quality, it is not on par
with LAME and other production-grade encoders quality-wise. Also, according to
the project&rsquo;s homepage, this encoder may not be free of bugs as the code was
written a long time ago and the project was dead for at least 5 years.
</p>
<p>This encoder only supports stereo and mono input. This is also CBR-only.
</p>
<p>The original project (last updated in early 2007) is at
<a href="http://sourceforge.net/projects/libshine-fxp/">http://sourceforge.net/projects/libshine-fxp/</a>. We only support the
updated fork by the Savonet/Liquidsoap project at <a href="https://github.com/savonet/shine">https://github.com/savonet/shine</a>.
</p>
<p>Requires the presence of the libshine headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libshine</code>.
</p>
<p>See also <a href="#libmp3lame">libmp3lame</a>.
</p>
<a name="Options-11"></a>
<h4 class="subsection">8.8.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-11" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-11" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libshine wrapper. The
<code>shineenc</code>-equivalent of the options are listed in parentheses.
</p>
<dl compact="compact">
<dt><samp>b (<em>-b</em>)</samp></dt>
<dd><p>Set bitrate expressed in bits/s for CBR. <code>shineenc</code> <samp>-b</samp> option
is expressed in kilobits/s.
</p>
</dd>
</dl>

<a name="libtwolame"></a>
<h3 class="section">8.9 libtwolame<span class="pull-right"><a class="anchor hidden-xs" href="#libtwolame" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libtwolame" aria-hidden="true">TOC</a></span></h3>

<p>TwoLAME MP2 encoder wrapper.
</p>
<p>Requires the presence of the libtwolame headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libtwolame</code>.
</p>
<a name="Options-12"></a>
<h4 class="subsection">8.9.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-12" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-12" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libtwolame wrapper. The
<code>twolame</code>-equivalent options follow the FFmpeg ones and are in
parentheses.
</p>
<dl compact="compact">
<dt><samp>b (<em>-b</em>)</samp></dt>
<dd><p>Set bitrate expressed in bits/s for CBR. <code>twolame</code> <samp>b</samp>
option is expressed in kilobits/s. Default value is 128k.
</p>
</dd>
<dt><samp>q (<em>-V</em>)</samp></dt>
<dd><p>Set quality for experimental VBR support. Maximum value range is
from -50 to 50, useful range is from -10 to 10. The higher the
value, the better the quality. This option is valid only using the
<code>ffmpeg</code> command-line tool. For library interface users,
use <samp>global_quality</samp>.
</p>
</dd>
<dt><samp>mode (<em>--mode</em>)</samp></dt>
<dd><p>Set the mode of the resulting audio. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>Choose mode automatically based on the input. This is the default.
</p></dd>
<dt>&lsquo;<samp>stereo</samp>&rsquo;</dt>
<dd><p>Stereo
</p></dd>
<dt>&lsquo;<samp>joint_stereo</samp>&rsquo;</dt>
<dd><p>Joint stereo
</p></dd>
<dt>&lsquo;<samp>dual_channel</samp>&rsquo;</dt>
<dd><p>Dual channel
</p></dd>
<dt>&lsquo;<samp>mono</samp>&rsquo;</dt>
<dd><p>Mono
</p></dd>
</dl>

</dd>
<dt><samp>psymodel (<em>--psyc-mode</em>)</samp></dt>
<dd><p>Set psychoacoustic model to use in encoding. The argument must be
an integer between -1 and 4, inclusive. The higher the value, the
better the quality. The default value is 3.
</p>
</dd>
<dt><samp>energy_levels (<em>--energy</em>)</samp></dt>
<dd><p>Enable energy levels extensions when set to 1. The default value is
0 (disabled).
</p>
</dd>
<dt><samp>error_protection (<em>--protect</em>)</samp></dt>
<dd><p>Enable CRC error protection when set to 1. The default value is 0
(disabled).
</p>
</dd>
<dt><samp>copyright (<em>--copyright</em>)</samp></dt>
<dd><p>Set MPEG audio copyright flag when set to 1. The default value is 0
(disabled).
</p>
</dd>
<dt><samp>original (<em>--original</em>)</samp></dt>
<dd><p>Set MPEG audio original flag when set to 1. The default value is 0
(disabled).
</p>
</dd>
</dl>

<a name="libvo_002daacenc"></a><a name="libvo_002daacenc-1"></a>
<h3 class="section">8.10 libvo-aacenc<span class="pull-right"><a class="anchor hidden-xs" href="#libvo_002daacenc-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libvo_002daacenc-1" aria-hidden="true">TOC</a></span></h3>

<p>VisualOn AAC encoder.
</p>
<p>Requires the presence of the libvo-aacenc headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libvo-aacenc --enable-version3</code>.
</p>
<p>This encoder is considered to be worse than the
<a href="#aacenc">native experimental FFmpeg AAC encoder</a>, according to
multiple sources.
</p>
<a name="Options-13"></a>
<h4 class="subsection">8.10.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-13" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-13" aria-hidden="true">TOC</a></span></h4>

<p>The VisualOn AAC encoder only support encoding AAC-LC and up to 2
channels. It is also CBR-only.
</p>
<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set bit rate in bits/s.
</p>
</dd>
</dl>

<a name="libvo_002damrwbenc"></a>
<h3 class="section">8.11 libvo-amrwbenc<span class="pull-right"><a class="anchor hidden-xs" href="#libvo_002damrwbenc" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libvo_002damrwbenc" aria-hidden="true">TOC</a></span></h3>

<p>VisualOn Adaptive Multi-Rate Wideband encoder.
</p>
<p>Requires the presence of the libvo-amrwbenc headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libvo-amrwbenc --enable-version3</code>.
</p>
<p>This is a mono-only encoder. Officially it only supports 16000Hz sample
rate, but you can override it by setting <samp>strict</samp> to
&lsquo;<samp>unofficial</samp>&rsquo; or lower.
</p>
<a name="Options-14"></a>
<h4 class="subsection">8.11.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-14" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-14" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set bitrate in bits/s. Only the following bitrates are supported, otherwise
libavcodec will round to the nearest valid bitrate.
</p>
<dl compact="compact">
<dt>&lsquo;<samp>6600</samp>&rsquo;</dt>
<dt>&lsquo;<samp>8850</samp>&rsquo;</dt>
<dt>&lsquo;<samp>12650</samp>&rsquo;</dt>
<dt>&lsquo;<samp>14250</samp>&rsquo;</dt>
<dt>&lsquo;<samp>15850</samp>&rsquo;</dt>
<dt>&lsquo;<samp>18250</samp>&rsquo;</dt>
<dt>&lsquo;<samp>19850</samp>&rsquo;</dt>
<dt>&lsquo;<samp>23050</samp>&rsquo;</dt>
<dt>&lsquo;<samp>23850</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>dtx</samp></dt>
<dd><p>Allow discontinuous transmission (generate comfort noise) when set to 1. The
default value is 0 (disabled).
</p>
</dd>
</dl>

<a name="libopus-1"></a>
<h3 class="section">8.12 libopus<span class="pull-right"><a class="anchor hidden-xs" href="#libopus-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopus-1" aria-hidden="true">TOC</a></span></h3>

<p>libopus Opus Interactive Audio Codec encoder wrapper.
</p>
<p>Requires the presence of the libopus headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libopus</code>.
</p>
<a name="Option-Mapping"></a>
<h4 class="subsection">8.12.1 Option Mapping<span class="pull-right"><a class="anchor hidden-xs" href="#Option-Mapping" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Option-Mapping" aria-hidden="true">TOC</a></span></h4>

<p>Most libopus options are modelled after the <code>opusenc</code> utility from
opus-tools. The following is an option mapping chart describing options
supported by the libopus wrapper, and their <code>opusenc</code>-equivalent
in parentheses.
</p>
<dl compact="compact">
<dt><samp>b (<em>bitrate</em>)</samp></dt>
<dd><p>Set the bit rate in bits/s.  FFmpeg&rsquo;s <samp>b</samp> option is
expressed in bits/s, while <code>opusenc</code>&rsquo;s <samp>bitrate</samp> in
kilobits/s.
</p>
</dd>
<dt><samp>vbr (<em>vbr</em>, <em>hard-cbr</em>, and <em>cvbr</em>)</samp></dt>
<dd><p>Set VBR mode. The FFmpeg <samp>vbr</samp> option has the following
valid arguments, with the <code>opusenc</code> equivalent options
in parentheses:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>off (<em>hard-cbr</em>)</samp>&rsquo;</dt>
<dd><p>Use constant bit rate encoding.
</p>
</dd>
<dt>&lsquo;<samp>on (<em>vbr</em>)</samp>&rsquo;</dt>
<dd><p>Use variable bit rate encoding (the default).
</p>
</dd>
<dt>&lsquo;<samp>constrained (<em>cvbr</em>)</samp>&rsquo;</dt>
<dd><p>Use constrained variable bit rate encoding.
</p></dd>
</dl>

</dd>
<dt><samp>compression_level (<em>comp</em>)</samp></dt>
<dd><p>Set encoding algorithm complexity. Valid options are integers in
the 0-10 range. 0 gives the fastest encodes but lower quality, while 10
gives the highest quality but slowest encoding. The default is 10.
</p>
</dd>
<dt><samp>frame_duration (<em>framesize</em>)</samp></dt>
<dd><p>Set maximum frame size, or duration of a frame in milliseconds. The
argument must be exactly the following: 2.5, 5, 10, 20, 40, 60. Smaller
frame sizes achieve lower latency but less quality at a given bitrate.
Sizes greater than 20ms are only interesting at fairly low bitrates.
The default is 20ms.
</p>
</dd>
<dt><samp>packet_loss (<em>expect-loss</em>)</samp></dt>
<dd><p>Set expected packet loss percentage. The default is 0.
</p>
</dd>
<dt><samp>application (N.A.)</samp></dt>
<dd><p>Set intended application type. Valid options are listed below:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>voip</samp>&rsquo;</dt>
<dd><p>Favor improved speech intelligibility.
</p></dd>
<dt>&lsquo;<samp>audio</samp>&rsquo;</dt>
<dd><p>Favor faithfulness to the input (the default).
</p></dd>
<dt>&lsquo;<samp>lowdelay</samp>&rsquo;</dt>
<dd><p>Restrict to only the lowest delay modes.
</p></dd>
</dl>

</dd>
<dt><samp>cutoff (N.A.)</samp></dt>
<dd><p>Set cutoff bandwidth in Hz. The argument must be exactly one of the
following: 4000, 6000, 8000, 12000, or 20000, corresponding to
narrowband, mediumband, wideband, super wideband, and fullband
respectively. The default is 0 (cutoff disabled).
</p>
</dd>
</dl>

<a name="libvorbis"></a>
<h3 class="section">8.13 libvorbis<span class="pull-right"><a class="anchor hidden-xs" href="#libvorbis" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libvorbis" aria-hidden="true">TOC</a></span></h3>

<p>libvorbis encoder wrapper.
</p>
<p>Requires the presence of the libvorbisenc headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libvorbis</code>.
</p>
<a name="Options-15"></a>
<h4 class="subsection">8.13.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-15" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-15" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libvorbis wrapper. The
<code>oggenc</code>-equivalent of the options are listed in parentheses.
</p>
<p>To get a more accurate and extensive documentation of the libvorbis
options, consult the libvorbisenc&rsquo;s and <code>oggenc</code>&rsquo;s documentations.
See <a href="http://xiph.org/vorbis/">http://xiph.org/vorbis/</a>,
<a href="http://wiki.xiph.org/Vorbis-tools">http://wiki.xiph.org/Vorbis-tools</a>, and oggenc(1).
</p>
<dl compact="compact">
<dt><samp>b (<em>-b</em>)</samp></dt>
<dd><p>Set bitrate expressed in bits/s for ABR. <code>oggenc</code> <samp>-b</samp> is
expressed in kilobits/s.
</p>
</dd>
<dt><samp>q (<em>-q</em>)</samp></dt>
<dd><p>Set constant quality setting for VBR. The value should be a float
number in the range of -1.0 to 10.0. The higher the value, the better
the quality. The default value is &lsquo;<samp>3.0</samp>&rsquo;.
</p>
<p>This option is valid only using the <code>ffmpeg</code> command-line tool.
For library interface users, use <samp>global_quality</samp>.
</p>
</dd>
<dt><samp>cutoff (<em>--advanced-encode-option lowpass_frequency=N</em>)</samp></dt>
<dd><p>Set cutoff bandwidth in Hz, a value of 0 disables cutoff. <code>oggenc</code>&rsquo;s
related option is expressed in kHz. The default value is &lsquo;<samp>0</samp>&rsquo; (cutoff
disabled).
</p>
</dd>
<dt><samp>minrate (<em>-m</em>)</samp></dt>
<dd><p>Set minimum bitrate expressed in bits/s. <code>oggenc</code> <samp>-m</samp> is
expressed in kilobits/s.
</p>
</dd>
<dt><samp>maxrate (<em>-M</em>)</samp></dt>
<dd><p>Set maximum bitrate expressed in bits/s. <code>oggenc</code> <samp>-M</samp> is
expressed in kilobits/s. This only has effect on ABR mode.
</p>
</dd>
<dt><samp>iblock (<em>--advanced-encode-option impulse_noisetune=N</em>)</samp></dt>
<dd><p>Set noise floor bias for impulse blocks. The value is a float number from
-15.0 to 0.0. A negative bias instructs the encoder to pay special attention
to the crispness of transients in the encoded audio. The tradeoff for better
transient response is a higher bitrate.
</p>
</dd>
</dl>

<a name="libwavpack"></a><a name="libwavpack-1"></a>
<h3 class="section">8.14 libwavpack<span class="pull-right"><a class="anchor hidden-xs" href="#libwavpack-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libwavpack-1" aria-hidden="true">TOC</a></span></h3>

<p>A wrapper providing WavPack encoding through libwavpack.
</p>
<p>Only lossless mode using 32-bit integer samples is supported currently.
</p>
<p>Requires the presence of the libwavpack headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libwavpack</code>.
</p>
<p>Note that a libavcodec-native encoder for the WavPack codec exists so users can
encode audios with this codec without using this encoder. See <a href="#wavpackenc">wavpackenc</a>.
</p>
<a name="Options-16"></a>
<h4 class="subsection">8.14.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-16" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-16" aria-hidden="true">TOC</a></span></h4>

<p><code>wavpack</code> command line utility&rsquo;s corresponding options are listed in
parentheses, if any.
</p>
<dl compact="compact">
<dt><samp>frame_size (<em>--blocksize</em>)</samp></dt>
<dd><p>Default is 32768.
</p>
</dd>
<dt><samp>compression_level</samp></dt>
<dd><p>Set speed vs. compression tradeoff. Acceptable arguments are listed below:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>0 (<em>-f</em>)</samp>&rsquo;</dt>
<dd><p>Fast mode.
</p>
</dd>
<dt>&lsquo;<samp>1</samp>&rsquo;</dt>
<dd><p>Normal (default) settings.
</p>
</dd>
<dt>&lsquo;<samp>2 (<em>-h</em>)</samp>&rsquo;</dt>
<dd><p>High quality.
</p>
</dd>
<dt>&lsquo;<samp>3 (<em>-hh</em>)</samp>&rsquo;</dt>
<dd><p>Very high quality.
</p>
</dd>
<dt>&lsquo;<samp>4-8 (<em>-hh -x</em><var>EXTRAPROC</var>)</samp>&rsquo;</dt>
<dd><p>Same as &lsquo;<samp>3</samp>&rsquo;, but with extra processing enabled.
</p>
<p>&lsquo;<samp>4</samp>&rsquo; is the same as <samp>-x2</samp> and &lsquo;<samp>8</samp>&rsquo; is the same as <samp>-x6</samp>.
</p>
</dd>
</dl>
</dd>
</dl>

<a name="wavpackenc"></a><a name="wavpack"></a>
<h3 class="section">8.15 wavpack<span class="pull-right"><a class="anchor hidden-xs" href="#wavpack" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-wavpack" aria-hidden="true">TOC</a></span></h3>

<p>WavPack lossless audio encoder.
</p>
<p>This is a libavcodec-native WavPack encoder. There is also an encoder based on
libwavpack, but there is virtually no reason to use that encoder.
</p>
<p>See also <a href="#libwavpack">libwavpack</a>.
</p>
<a name="Options-17"></a>
<h4 class="subsection">8.15.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-17" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-17" aria-hidden="true">TOC</a></span></h4>

<p>The equivalent options for <code>wavpack</code> command line utility are listed in
parentheses.
</p>
<a name="Shared-options"></a>
<h4 class="subsubsection">8.15.1.1 Shared options<span class="pull-right"><a class="anchor hidden-xs" href="#Shared-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Shared-options" aria-hidden="true">TOC</a></span></h4>

<p>The following shared options are effective for this encoder. Only special notes
about this particular encoder will be documented here. For the general meaning
of the options, see <a href="#codec_002doptions">the Codec Options chapter</a>.
</p>
<dl compact="compact">
<dt><samp>frame_size (<em>--blocksize</em>)</samp></dt>
<dd><p>For this encoder, the range for this option is between 128 and 131072. Default
is automatically decided based on sample rate and number of channel.
</p>
<p>For the complete formula of calculating default, see
<samp>libavcodec/wavpackenc.c</samp>.
</p>
</dd>
<dt><samp>compression_level (<em>-f</em>, <em>-h</em>, <em>-hh</em>, and <em>-x</em>)</samp></dt>
<dd><p>This option&rsquo;s syntax is consistent with <a href="#libwavpack">libwavpack</a>&rsquo;s.
</p></dd>
</dl>

<a name="Private-options"></a>
<h4 class="subsubsection">8.15.1.2 Private options<span class="pull-right"><a class="anchor hidden-xs" href="#Private-options" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Private-options" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>joint_stereo (<em>-j</em>)</samp></dt>
<dd><p>Set whether to enable joint stereo. Valid values are:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>on (<em>1</em>)</samp>&rsquo;</dt>
<dd><p>Force mid/side audio encoding.
</p></dd>
<dt>&lsquo;<samp>off (<em>0</em>)</samp>&rsquo;</dt>
<dd><p>Force left/right audio encoding.
</p></dd>
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>Let the encoder decide automatically.
</p></dd>
</dl>

</dd>
<dt><samp>optimize_mono</samp></dt>
<dd><p>Set whether to enable optimization for mono. This option is only effective for
non-mono streams. Available values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>on</samp>&rsquo;</dt>
<dd><p>enabled
</p></dd>
<dt>&lsquo;<samp>off</samp>&rsquo;</dt>
<dd><p>disabled
</p></dd>
</dl>

</dd>
</dl>


<a name="Video-Encoders"></a>
<h2 class="chapter">9 Video Encoders<span class="pull-right"><a class="anchor hidden-xs" href="#Video-Encoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Video-Encoders" aria-hidden="true">TOC</a></span></h2>

<p>A description of some of the currently available video encoders
follows.
</p>
<a name="libopenh264"></a>
<h3 class="section">9.1 libopenh264<span class="pull-right"><a class="anchor hidden-xs" href="#libopenh264" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libopenh264" aria-hidden="true">TOC</a></span></h3>

<p>Cisco libopenh264 H.264/MPEG-4 AVC encoder wrapper.
</p>
<p>This encoder requires the presence of the libopenh264 headers and
library during configuration. You need to explicitly configure the
build with <code>--enable-libopenh264</code>. The library is detected using
<code>pkg-config</code>.
</p>
<p>For more information about the library see
<a href="http://www.openh264.org">http://www.openh264.org</a>.
</p>
<a name="Options-18"></a>
<h4 class="subsection">9.1.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-18" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-18" aria-hidden="true">TOC</a></span></h4>

<p>The following FFmpeg global options affect the configurations of the
libopenh264 encoder.
</p>
<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set the bitrate (as a number of bits per second).
</p>
</dd>
<dt><samp>g</samp></dt>
<dd><p>Set the GOP size.
</p>
</dd>
<dt><samp>maxrate</samp></dt>
<dd><p>Set the max bitrate (as a number of bits per second).
</p>
</dd>
<dt><samp>flags +global_header</samp></dt>
<dd><p>Set global header in the bitstream.
</p>
</dd>
<dt><samp>slices</samp></dt>
<dd><p>Set the number of slices, used in parallelized encoding. Default value
is 0. This is only used when <samp>slice_mode</samp> is set to
&lsquo;<samp>fixed</samp>&rsquo;.
</p>
</dd>
<dt><samp>slice_mode</samp></dt>
<dd><p>Set slice mode. Can assume one of the follwing possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>fixed</samp>&rsquo;</dt>
<dd><p>a fixed number of slices
</p></dd>
<dt>&lsquo;<samp>rowmb</samp>&rsquo;</dt>
<dd><p>one slice per row of macroblocks
</p></dd>
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dd><p>automatic number of slices according to number of thread
</p></dd>
</dl>

<p>Default value is &lsquo;<samp>auto</samp>&rsquo;.
</p>
</dd>
<dt><samp>loopfilter</samp></dt>
<dd><p>Enable loop filter, if set to 1 (automatically enabled). To disable
set a value of 0.
</p>
</dd>
<dt><samp>profile</samp></dt>
<dd><p>Set profile restrictions. If set to the value of &lsquo;<samp>main</samp>&rsquo; enable
CABAC (set the <code>SEncParamExt.iEntropyCodingModeFlag</code> flag to 1).
</p></dd>
</dl>

<a name="jpeg2000"></a>
<h3 class="section">9.2 jpeg2000<span class="pull-right"><a class="anchor hidden-xs" href="#jpeg2000" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-jpeg2000" aria-hidden="true">TOC</a></span></h3>

<p>The native jpeg 2000 encoder is lossy by default, the <code>-q:v</code>
option can be used to set the encoding quality. Lossless encoding
can be selected with <code>-pred 1</code>.
</p>
<a name="Options-19"></a>
<h4 class="subsection">9.2.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-19" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-19" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>format</samp></dt>
<dd><p>Can be set to either <code>j2k</code> or <code>jp2</code> (the default) that
makes it possible to store non-rgb pix_fmts.
</p>
</dd>
</dl>

<a name="snow"></a>
<h3 class="section">9.3 snow<span class="pull-right"><a class="anchor hidden-xs" href="#snow" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-snow" aria-hidden="true">TOC</a></span></h3>

<a name="Options-20"></a>
<h4 class="subsection">9.3.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-20" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-20" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>iterative_dia_size</samp></dt>
<dd><p>dia size for the iterative motion estimation
</p></dd>
</dl>

<a name="libtheora"></a>
<h3 class="section">9.4 libtheora<span class="pull-right"><a class="anchor hidden-xs" href="#libtheora" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libtheora" aria-hidden="true">TOC</a></span></h3>

<p>libtheora Theora encoder wrapper.
</p>
<p>Requires the presence of the libtheora headers and library during
configuration. You need to explicitly configure the build with
<code>--enable-libtheora</code>.
</p>
<p>For more information about the libtheora project see
<a href="http://www.theora.org/">http://www.theora.org/</a>.
</p>
<a name="Options-21"></a>
<h4 class="subsection">9.4.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-21" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-21" aria-hidden="true">TOC</a></span></h4>

<p>The following global options are mapped to internal libtheora options
which affect the quality and the bitrate of the encoded stream.
</p>
<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set the video bitrate in bit/s for CBR (Constant Bit Rate) mode.  In
case VBR (Variable Bit Rate) mode is enabled this option is ignored.
</p>
</dd>
<dt><samp>flags</samp></dt>
<dd><p>Used to enable constant quality mode (VBR) encoding through the
<samp>qscale</samp> flag, and to enable the <code>pass1</code> and <code>pass2</code>
modes.
</p>
</dd>
<dt><samp>g</samp></dt>
<dd><p>Set the GOP size.
</p>
</dd>
<dt><samp>global_quality</samp></dt>
<dd><p>Set the global quality as an integer in lambda units.
</p>
<p>Only relevant when VBR mode is enabled with <code>flags +qscale</code>. The
value is converted to QP units by dividing it by <code>FF_QP2LAMBDA</code>,
clipped in the [0 - 10] range, and then multiplied by 6.3 to get a
value in the native libtheora range [0-63]. A higher value corresponds
to a higher quality.
</p>
</dd>
<dt><samp>q</samp></dt>
<dd><p>Enable VBR mode when set to a non-negative value, and set constant
quality value as a double floating point value in QP units.
</p>
<p>The value is clipped in the [0-10] range, and then multiplied by 6.3
to get a value in the native libtheora range [0-63].
</p>
<p>This option is valid only using the <code>ffmpeg</code> command-line
tool. For library interface users, use <samp>global_quality</samp>.
</p></dd>
</dl>

<a name="Examples-2"></a>
<h4 class="subsection">9.4.2 Examples<span class="pull-right"><a class="anchor hidden-xs" href="#Examples-2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Examples-2" aria-hidden="true">TOC</a></span></h4>

<ul>
<li> Set maximum constant quality (VBR) encoding with <code>ffmpeg</code>:
<div class="example">
<pre class="example">ffmpeg -i INPUT -codec:v libtheora -q:v 10 OUTPUT.ogg
</pre></div>

</li><li> Use <code>ffmpeg</code> to convert a CBR 1000 kbps Theora video stream:
<div class="example">
<pre class="example">ffmpeg -i INPUT -codec:v libtheora -b:v 1000k OUTPUT.ogg
</pre></div>
</li></ul>

<a name="libvpx"></a>
<h3 class="section">9.5 libvpx<span class="pull-right"><a class="anchor hidden-xs" href="#libvpx" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libvpx" aria-hidden="true">TOC</a></span></h3>

<p>VP8/VP9 format supported through libvpx.
</p>
<p>Requires the presence of the libvpx headers and library during configuration.
You need to explicitly configure the build with <code>--enable-libvpx</code>.
</p>
<a name="Options-22"></a>
<h4 class="subsection">9.5.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-22" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-22" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libvpx wrapper. The
<code>vpxenc</code>-equivalent options or values are listed in parentheses
for easy migration.
</p>
<p>To reduce the duplication of documentation, only the private options
and some others requiring special attention are documented here. For
the documentation of the undocumented generic options, see
<a href="#codec_002doptions">the Codec Options chapter</a>.
</p>
<p>To get more documentation of the libvpx options, invoke the command
<code>ffmpeg -h encoder=libvpx</code>, <code>ffmpeg -h encoder=libvpx-vp9</code> or
<code>vpxenc --help</code>. Further information is available in the libvpx API
documentation.
</p>
<dl compact="compact">
<dt><samp>b (<em>target-bitrate</em>)</samp></dt>
<dd><p>Set bitrate in bits/s. Note that FFmpeg&rsquo;s <samp>b</samp> option is
expressed in bits/s, while <code>vpxenc</code>&rsquo;s <samp>target-bitrate</samp> is in
kilobits/s.
</p>
</dd>
<dt><samp>g (<em>kf-max-dist</em>)</samp></dt>
<dt><samp>keyint_min (<em>kf-min-dist</em>)</samp></dt>
<dt><samp>qmin (<em>min-q</em>)</samp></dt>
<dt><samp>qmax (<em>max-q</em>)</samp></dt>
<dt><samp>bufsize (<em>buf-sz</em>, <em>buf-optimal-sz</em>)</samp></dt>
<dd><p>Set ratecontrol buffer size (in bits). Note <code>vpxenc</code>&rsquo;s options are
specified in milliseconds, the libvpx wrapper converts this value as follows:
<code>buf-sz = bufsize * 1000 / bitrate</code>,
<code>buf-optimal-sz = bufsize * 1000 / bitrate * 5 / 6</code>.
</p>
</dd>
<dt><samp>rc_init_occupancy (<em>buf-initial-sz</em>)</samp></dt>
<dd><p>Set number of bits which should be loaded into the rc buffer before decoding
starts. Note <code>vpxenc</code>&rsquo;s option is specified in milliseconds, the libvpx
wrapper converts this value as follows:
<code>rc_init_occupancy * 1000 / bitrate</code>.
</p>
</dd>
<dt><samp>undershoot-pct</samp></dt>
<dd><p>Set datarate undershoot (min) percentage of the target bitrate.
</p>
</dd>
<dt><samp>overshoot-pct</samp></dt>
<dd><p>Set datarate overshoot (max) percentage of the target bitrate.
</p>
</dd>
<dt><samp>skip_threshold (<em>drop-frame</em>)</samp></dt>
<dt><samp>qcomp (<em>bias-pct</em>)</samp></dt>
<dt><samp>maxrate (<em>maxsection-pct</em>)</samp></dt>
<dd><p>Set GOP max bitrate in bits/s. Note <code>vpxenc</code>&rsquo;s option is specified as a
percentage of the target bitrate, the libvpx wrapper converts this value as
follows: <code>(maxrate * 100 / bitrate)</code>.
</p>
</dd>
<dt><samp>minrate (<em>minsection-pct</em>)</samp></dt>
<dd><p>Set GOP min bitrate in bits/s. Note <code>vpxenc</code>&rsquo;s option is specified as a
percentage of the target bitrate, the libvpx wrapper converts this value as
follows: <code>(minrate * 100 / bitrate)</code>.
</p>
</dd>
<dt><samp>minrate, maxrate, b <em>end-usage=cbr</em></samp></dt>
<dd><p><code>(minrate == maxrate == bitrate)</code>.
</p>
</dd>
<dt><samp>crf (<em>end-usage=cq</em>, <em>cq-level</em>)</samp></dt>
<dt><samp>quality, deadline (<em>deadline</em>)</samp></dt>
<dd><dl compact="compact">
<dt>&lsquo;<samp>best</samp>&rsquo;</dt>
<dd><p>Use best quality deadline. Poorly named and quite slow, this option should be
avoided as it may give worse quality output than good.
</p></dd>
<dt>&lsquo;<samp>good</samp>&rsquo;</dt>
<dd><p>Use good quality deadline. This is a good trade-off between speed and quality
when used with the <samp>cpu-used</samp> option.
</p></dd>
<dt>&lsquo;<samp>realtime</samp>&rsquo;</dt>
<dd><p>Use realtime quality deadline.
</p></dd>
</dl>

</dd>
<dt><samp>speed, cpu-used (<em>cpu-used</em>)</samp></dt>
<dd><p>Set quality/speed ratio modifier. Higher values speed up the encode at the cost
of quality.
</p>
</dd>
<dt><samp>nr (<em>noise-sensitivity</em>)</samp></dt>
<dt><samp>static-thresh</samp></dt>
<dd><p>Set a change threshold on blocks below which they will be skipped by the
encoder.
</p>
</dd>
<dt><samp>slices (<em>token-parts</em>)</samp></dt>
<dd><p>Note that FFmpeg&rsquo;s <samp>slices</samp> option gives the total number of partitions,
while <code>vpxenc</code>&rsquo;s <samp>token-parts</samp> is given as
<code>log2(partitions)</code>.
</p>
</dd>
<dt><samp>max-intra-rate</samp></dt>
<dd><p>Set maximum I-frame bitrate as a percentage of the target bitrate. A value of 0
means unlimited.
</p>
</dd>
<dt><samp>force_key_frames</samp></dt>
<dd><p><code>VPX_EFLAG_FORCE_KF</code>
</p>
</dd>
<dt><samp>Alternate reference frame related</samp></dt>
<dd><dl compact="compact">
<dt><samp>auto-alt-ref</samp></dt>
<dd><p>Enable use of alternate reference frames (2-pass only).
</p></dd>
<dt><samp>arnr-max-frames</samp></dt>
<dd><p>Set altref noise reduction max frame count.
</p></dd>
<dt><samp>arnr-type</samp></dt>
<dd><p>Set altref noise reduction filter type: backward, forward, centered.
</p></dd>
<dt><samp>arnr-strength</samp></dt>
<dd><p>Set altref noise reduction filter strength.
</p></dd>
<dt><samp>rc-lookahead, lag-in-frames (<em>lag-in-frames</em>)</samp></dt>
<dd><p>Set number of frames to look ahead for frametype and ratecontrol.
</p></dd>
</dl>

</dd>
<dt><samp>error-resilient</samp></dt>
<dd><p>Enable error resiliency features.
</p>
</dd>
<dt><samp>VP9-specific options</samp></dt>
<dd><dl compact="compact">
<dt><samp>lossless</samp></dt>
<dd><p>Enable lossless mode.
</p></dd>
<dt><samp>tile-columns</samp></dt>
<dd><p>Set number of tile columns to use. Note this is given as
<code>log2(tile_columns)</code>. For example, 8 tile columns would be requested by
setting the <samp>tile-columns</samp> option to 3.
</p></dd>
<dt><samp>tile-rows</samp></dt>
<dd><p>Set number of tile rows to use. Note this is given as <code>log2(tile_rows)</code>.
For example, 4 tile rows would be requested by setting the <samp>tile-rows</samp>
option to 2.
</p></dd>
<dt><samp>frame-parallel</samp></dt>
<dd><p>Enable frame parallel decodability features.
</p></dd>
<dt><samp>aq-mode</samp></dt>
<dd><p>Set adaptive quantization mode (0: off (default), 1: variance 2: complexity, 3:
cyclic refresh).
</p></dd>
<dt><samp>colorspace <em>color-space</em></samp></dt>
<dd><p>Set input color space. The VP9 bitstream supports signaling the following
colorspaces:
</p><dl compact="compact">
<dt><samp>&lsquo;<samp>rgb</samp>&rsquo; <em>sRGB</em></samp></dt>
<dt><samp>&lsquo;<samp>bt709</samp>&rsquo; <em>bt709</em></samp></dt>
<dt><samp>&lsquo;<samp>unspecified</samp>&rsquo; <em>unknown</em></samp></dt>
<dt><samp>&lsquo;<samp>bt470bg</samp>&rsquo; <em>bt601</em></samp></dt>
<dt><samp>&lsquo;<samp>smpte170m</samp>&rsquo; <em>smpte170</em></samp></dt>
<dt><samp>&lsquo;<samp>smpte240m</samp>&rsquo; <em>smpte240</em></samp></dt>
<dt><samp>&lsquo;<samp>bt2020_ncl</samp>&rsquo; <em>bt2020</em></samp></dt>
</dl>
</dd>
</dl>

</dd>
</dl>

<p>For more information about libvpx see:
<a href="http://www.webmproject.org/">http://www.webmproject.org/</a>
</p>

<a name="libwebp"></a>
<h3 class="section">9.6 libwebp<span class="pull-right"><a class="anchor hidden-xs" href="#libwebp" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libwebp" aria-hidden="true">TOC</a></span></h3>

<p>libwebp WebP Image encoder wrapper
</p>
<p>libwebp is Google&rsquo;s official encoder for WebP images. It can encode in either
lossy or lossless mode. Lossy images are essentially a wrapper around a VP8
frame. Lossless images are a separate codec developed by Google.
</p>
<a name="Pixel-Format"></a>
<h4 class="subsection">9.6.1 Pixel Format<span class="pull-right"><a class="anchor hidden-xs" href="#Pixel-Format" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Pixel-Format" aria-hidden="true">TOC</a></span></h4>

<p>Currently, libwebp only supports YUV420 for lossy and RGB for lossless due
to limitations of the format and libwebp. Alpha is supported for either mode.
Because of API limitations, if RGB is passed in when encoding lossy or YUV is
passed in for encoding lossless, the pixel format will automatically be
converted using functions from libwebp. This is not ideal and is done only for
convenience.
</p>
<a name="Options-23"></a>
<h4 class="subsection">9.6.2 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-23" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-23" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>-lossless <var>boolean</var></samp></dt>
<dd><p>Enables/Disables use of lossless mode. Default is 0.
</p>
</dd>
<dt><samp>-compression_level <var>integer</var></samp></dt>
<dd><p>For lossy, this is a quality/speed tradeoff. Higher values give better quality
for a given size at the cost of increased encoding time. For lossless, this is
a size/speed tradeoff. Higher values give smaller size at the cost of increased
encoding time. More specifically, it controls the number of extra algorithms
and compression tools used, and varies the combination of these tools. This
maps to the <var>method</var> option in libwebp. The valid range is 0 to 6.
Default is 4.
</p>
</dd>
<dt><samp>-qscale <var>float</var></samp></dt>
<dd><p>For lossy encoding, this controls image quality, 0 to 100. For lossless
encoding, this controls the effort and time spent at compressing more. The
default value is 75. Note that for usage via libavcodec, this option is called
<var>global_quality</var> and must be multiplied by <var>FF_QP2LAMBDA</var>.
</p>
</dd>
<dt><samp>-preset <var>type</var></samp></dt>
<dd><p>Configuration preset. This does some automatic settings based on the general
type of the image.
</p><dl compact="compact">
<dt><samp>none</samp></dt>
<dd><p>Do not use a preset.
</p></dd>
<dt><samp>default</samp></dt>
<dd><p>Use the encoder default.
</p></dd>
<dt><samp>picture</samp></dt>
<dd><p>Digital picture, like portrait, inner shot
</p></dd>
<dt><samp>photo</samp></dt>
<dd><p>Outdoor photograph, with natural lighting
</p></dd>
<dt><samp>drawing</samp></dt>
<dd><p>Hand or line drawing, with high-contrast details
</p></dd>
<dt><samp>icon</samp></dt>
<dd><p>Small-sized colorful images
</p></dd>
<dt><samp>text</samp></dt>
<dd><p>Text-like
</p></dd>
</dl>

</dd>
</dl>

<a name="libx264_002c-libx264rgb"></a>
<h3 class="section">9.7 libx264, libx264rgb<span class="pull-right"><a class="anchor hidden-xs" href="#libx264_002c-libx264rgb" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libx264_002c-libx264rgb" aria-hidden="true">TOC</a></span></h3>

<p>x264 H.264/MPEG-4 AVC encoder wrapper.
</p>
<p>This encoder requires the presence of the libx264 headers and library
during configuration. You need to explicitly configure the build with
<code>--enable-libx264</code>.
</p>
<p>libx264 supports an impressive number of features, including 8x8 and
4x4 adaptive spatial transform, adaptive B-frame placement, CAVLC/CABAC
entropy coding, interlacing (MBAFF), lossless mode, psy optimizations
for detail retention (adaptive quantization, psy-RD, psy-trellis).
</p>
<p>Many libx264 encoder options are mapped to FFmpeg global codec
options, while unique encoder options are provided through private
options. Additionally the <samp>x264opts</samp> and <samp>x264-params</samp>
private options allows one to pass a list of key=value tuples as accepted
by the libx264 <code>x264_param_parse</code> function.
</p>
<p>The x264 project website is at
<a href="http://www.videolan.org/developers/x264.html">http://www.videolan.org/developers/x264.html</a>.
</p>
<p>The libx264rgb encoder is the same as libx264, except it accepts packed RGB
pixel formats as input instead of YUV.
</p>
<a name="Supported-Pixel-Formats"></a>
<h4 class="subsection">9.7.1 Supported Pixel Formats<span class="pull-right"><a class="anchor hidden-xs" href="#Supported-Pixel-Formats" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Supported-Pixel-Formats" aria-hidden="true">TOC</a></span></h4>

<p>x264 supports 8- to 10-bit color spaces. The exact bit depth is controlled at
x264&rsquo;s configure time. FFmpeg only supports one bit depth in one particular
build. In other words, it is not possible to build one FFmpeg with multiple
versions of x264 with different bit depths.
</p>
<a name="Options-24"></a>
<h4 class="subsection">9.7.2 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-24" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-24" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libx264 wrapper. The
<code>x264</code>-equivalent options or values are listed in parentheses
for easy migration.
</p>
<p>To reduce the duplication of documentation, only the private options
and some others requiring special attention are documented here. For
the documentation of the undocumented generic options, see
<a href="#codec_002doptions">the Codec Options chapter</a>.
</p>
<p>To get a more accurate and extensive documentation of the libx264
options, invoke the command <code>x264 --full-help</code> or consult
the libx264 documentation.
</p>
<dl compact="compact">
<dt><samp>b (<em>bitrate</em>)</samp></dt>
<dd><p>Set bitrate in bits/s. Note that FFmpeg&rsquo;s <samp>b</samp> option is
expressed in bits/s, while <code>x264</code>&rsquo;s <samp>bitrate</samp> is in
kilobits/s.
</p>
</dd>
<dt><samp>bf (<em>bframes</em>)</samp></dt>
<dt><samp>g (<em>keyint</em>)</samp></dt>
<dt><samp>qmin (<em>qpmin</em>)</samp></dt>
<dd><p>Minimum quantizer scale.
</p>
</dd>
<dt><samp>qmax (<em>qpmax</em>)</samp></dt>
<dd><p>Maximum quantizer scale.
</p>
</dd>
<dt><samp>qdiff (<em>qpstep</em>)</samp></dt>
<dd><p>Maximum difference between quantizer scales.
</p>
</dd>
<dt><samp>qblur (<em>qblur</em>)</samp></dt>
<dd><p>Quantizer curve blur
</p>
</dd>
<dt><samp>qcomp (<em>qcomp</em>)</samp></dt>
<dd><p>Quantizer curve compression factor
</p>
</dd>
<dt><samp>refs (<em>ref</em>)</samp></dt>
<dd><p>Number of reference frames each P-frame can use. The range is from <var>0-16</var>.
</p>
</dd>
<dt><samp>sc_threshold (<em>scenecut</em>)</samp></dt>
<dd><p>Sets the threshold for the scene change detection.
</p>
</dd>
<dt><samp>trellis (<em>trellis</em>)</samp></dt>
<dd><p>Performs Trellis quantization to increase efficiency. Enabled by default.
</p>
</dd>
<dt><samp>nr  (<em>nr</em>)</samp></dt>
<dt><samp>me_range (<em>merange</em>)</samp></dt>
<dd><p>Maximum range of the motion search in pixels.
</p>
</dd>
<dt><samp>me_method (<em>me</em>)</samp></dt>
<dd><p>Set motion estimation method. Possible values in the decreasing order
of speed:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>dia (<em>dia</em>)</samp>&rsquo;</dt>
<dt>&lsquo;<samp>epzs (<em>dia</em>)</samp>&rsquo;</dt>
<dd><p>Diamond search with radius 1 (fastest). &lsquo;<samp>epzs</samp>&rsquo; is an alias for
&lsquo;<samp>dia</samp>&rsquo;.
</p></dd>
<dt>&lsquo;<samp>hex (<em>hex</em>)</samp>&rsquo;</dt>
<dd><p>Hexagonal search with radius 2.
</p></dd>
<dt>&lsquo;<samp>umh (<em>umh</em>)</samp>&rsquo;</dt>
<dd><p>Uneven multi-hexagon search.
</p></dd>
<dt>&lsquo;<samp>esa (<em>esa</em>)</samp>&rsquo;</dt>
<dd><p>Exhaustive search.
</p></dd>
<dt>&lsquo;<samp>tesa (<em>tesa</em>)</samp>&rsquo;</dt>
<dd><p>Hadamard exhaustive search (slowest).
</p></dd>
</dl>

</dd>
<dt><samp>subq (<em>subme</em>)</samp></dt>
<dd><p>Sub-pixel motion estimation method.
</p>
</dd>
<dt><samp>b_strategy (<em>b-adapt</em>)</samp></dt>
<dd><p>Adaptive B-frame placement decision algorithm. Use only on first-pass.
</p>
</dd>
<dt><samp>keyint_min (<em>min-keyint</em>)</samp></dt>
<dd><p>Minimum GOP size.
</p>
</dd>
<dt><samp>coder</samp></dt>
<dd><p>Set entropy encoder. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>ac</samp>&rsquo;</dt>
<dd><p>Enable CABAC.
</p>
</dd>
<dt>&lsquo;<samp>vlc</samp>&rsquo;</dt>
<dd><p>Enable CAVLC and disable CABAC. It generates the same effect as
<code>x264</code>&rsquo;s <samp>--no-cabac</samp> option.
</p></dd>
</dl>

</dd>
<dt><samp>cmp</samp></dt>
<dd><p>Set full pixel motion estimation comparation algorithm. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>chroma</samp>&rsquo;</dt>
<dd><p>Enable chroma in motion estimation.
</p>
</dd>
<dt>&lsquo;<samp>sad</samp>&rsquo;</dt>
<dd><p>Ignore chroma in motion estimation. It generates the same effect as
<code>x264</code>&rsquo;s <samp>--no-chroma-me</samp> option.
</p></dd>
</dl>

</dd>
<dt><samp>threads (<em>threads</em>)</samp></dt>
<dd><p>Number of encoding threads.
</p>
</dd>
<dt><samp>thread_type</samp></dt>
<dd><p>Set multithreading technique. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>slice</samp>&rsquo;</dt>
<dd><p>Slice-based multithreading. It generates the same effect as
<code>x264</code>&rsquo;s <samp>--sliced-threads</samp> option.
</p></dd>
<dt>&lsquo;<samp>frame</samp>&rsquo;</dt>
<dd><p>Frame-based multithreading.
</p></dd>
</dl>

</dd>
<dt><samp>flags</samp></dt>
<dd><p>Set encoding flags. It can be used to disable closed GOP and enable
open GOP by setting it to <code>-cgop</code>. The result is similar to
the behavior of <code>x264</code>&rsquo;s <samp>--open-gop</samp> option.
</p>
</dd>
<dt><samp>rc_init_occupancy (<em>vbv-init</em>)</samp></dt>
<dt><samp>preset (<em>preset</em>)</samp></dt>
<dd><p>Set the encoding preset.
</p>
</dd>
<dt><samp>tune (<em>tune</em>)</samp></dt>
<dd><p>Set tuning of the encoding params.
</p>
</dd>
<dt><samp>profile (<em>profile</em>)</samp></dt>
<dd><p>Set profile restrictions.
</p>
</dd>
<dt><samp>fastfirstpass</samp></dt>
<dd><p>Enable fast settings when encoding first pass, when set to 1. When set
to 0, it has the same effect of <code>x264</code>&rsquo;s
<samp>--slow-firstpass</samp> option.
</p>
</dd>
<dt><samp>crf (<em>crf</em>)</samp></dt>
<dd><p>Set the quality for constant quality mode.
</p>
</dd>
<dt><samp>crf_max (<em>crf-max</em>)</samp></dt>
<dd><p>In CRF mode, prevents VBV from lowering quality beyond this point.
</p>
</dd>
<dt><samp>qp (<em>qp</em>)</samp></dt>
<dd><p>Set constant quantization rate control method parameter.
</p>
</dd>
<dt><samp>aq-mode (<em>aq-mode</em>)</samp></dt>
<dd><p>Set AQ method. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>none (<em>0</em>)</samp>&rsquo;</dt>
<dd><p>Disabled.
</p>
</dd>
<dt>&lsquo;<samp>variance (<em>1</em>)</samp>&rsquo;</dt>
<dd><p>Variance AQ (complexity mask).
</p>
</dd>
<dt>&lsquo;<samp>autovariance (<em>2</em>)</samp>&rsquo;</dt>
<dd><p>Auto-variance AQ (experimental).
</p></dd>
</dl>

</dd>
<dt><samp>aq-strength (<em>aq-strength</em>)</samp></dt>
<dd><p>Set AQ strength, reduce blocking and blurring in flat and textured areas.
</p>
</dd>
<dt><samp>psy</samp></dt>
<dd><p>Use psychovisual optimizations when set to 1. When set to 0, it has the
same effect as <code>x264</code>&rsquo;s <samp>--no-psy</samp> option.
</p>
</dd>
<dt><samp>psy-rd  (<em>psy-rd</em>)</samp></dt>
<dd><p>Set strength of psychovisual optimization, in
<var>psy-rd</var>:<var>psy-trellis</var> format.
</p>
</dd>
<dt><samp>rc-lookahead (<em>rc-lookahead</em>)</samp></dt>
<dd><p>Set number of frames to look ahead for frametype and ratecontrol.
</p>
</dd>
<dt><samp>weightb</samp></dt>
<dd><p>Enable weighted prediction for B-frames when set to 1. When set to 0,
it has the same effect as <code>x264</code>&rsquo;s <samp>--no-weightb</samp> option.
</p>
</dd>
<dt><samp>weightp (<em>weightp</em>)</samp></dt>
<dd><p>Set weighted prediction method for P-frames. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>none (<em>0</em>)</samp>&rsquo;</dt>
<dd><p>Disabled
</p></dd>
<dt>&lsquo;<samp>simple (<em>1</em>)</samp>&rsquo;</dt>
<dd><p>Enable only weighted refs
</p></dd>
<dt>&lsquo;<samp>smart (<em>2</em>)</samp>&rsquo;</dt>
<dd><p>Enable both weighted refs and duplicates
</p></dd>
</dl>

</dd>
<dt><samp>ssim (<em>ssim</em>)</samp></dt>
<dd><p>Enable calculation and printing SSIM stats after the encoding.
</p>
</dd>
<dt><samp>intra-refresh (<em>intra-refresh</em>)</samp></dt>
<dd><p>Enable the use of Periodic Intra Refresh instead of IDR frames when set
to 1.
</p>
</dd>
<dt><samp>avcintra-class (<em>class</em>)</samp></dt>
<dd><p>Configure the encoder to generate AVC-Intra.
Valid values are 50,100 and 200
</p>
</dd>
<dt><samp>bluray-compat (<em>bluray-compat</em>)</samp></dt>
<dd><p>Configure the encoder to be compatible with the bluray standard.
It is a shorthand for setting &quot;bluray-compat=1 force-cfr=1&quot;.
</p>
</dd>
<dt><samp>b-bias (<em>b-bias</em>)</samp></dt>
<dd><p>Set the influence on how often B-frames are used.
</p>
</dd>
<dt><samp>b-pyramid (<em>b-pyramid</em>)</samp></dt>
<dd><p>Set method for keeping of some B-frames as references. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>none (<em>none</em>)</samp>&rsquo;</dt>
<dd><p>Disabled.
</p></dd>
<dt>&lsquo;<samp>strict (<em>strict</em>)</samp>&rsquo;</dt>
<dd><p>Strictly hierarchical pyramid.
</p></dd>
<dt>&lsquo;<samp>normal (<em>normal</em>)</samp>&rsquo;</dt>
<dd><p>Non-strict (not Blu-ray compatible).
</p></dd>
</dl>

</dd>
<dt><samp>mixed-refs</samp></dt>
<dd><p>Enable the use of one reference per partition, as opposed to one
reference per macroblock when set to 1. When set to 0, it has the
same effect as <code>x264</code>&rsquo;s <samp>--no-mixed-refs</samp> option.
</p>
</dd>
<dt><samp>8x8dct</samp></dt>
<dd><p>Enable adaptive spatial transform (high profile 8x8 transform)
when set to 1. When set to 0, it has the same effect as
<code>x264</code>&rsquo;s <samp>--no-8x8dct</samp> option.
</p>
</dd>
<dt><samp>fast-pskip</samp></dt>
<dd><p>Enable early SKIP detection on P-frames when set to 1. When set
to 0, it has the same effect as <code>x264</code>&rsquo;s
<samp>--no-fast-pskip</samp> option.
</p>
</dd>
<dt><samp>aud (<em>aud</em>)</samp></dt>
<dd><p>Enable use of access unit delimiters when set to 1.
</p>
</dd>
<dt><samp>mbtree</samp></dt>
<dd><p>Enable use macroblock tree ratecontrol when set to 1. When set
to 0, it has the same effect as <code>x264</code>&rsquo;s
<samp>--no-mbtree</samp> option.
</p>
</dd>
<dt><samp>deblock (<em>deblock</em>)</samp></dt>
<dd><p>Set loop filter parameters, in <var>alpha</var>:<var>beta</var> form.
</p>
</dd>
<dt><samp>cplxblur (<em>cplxblur</em>)</samp></dt>
<dd><p>Set fluctuations reduction in QP (before curve compression).
</p>
</dd>
<dt><samp>partitions (<em>partitions</em>)</samp></dt>
<dd><p>Set partitions to consider as a comma-separated list of. Possible
values in the list:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>p8x8</samp>&rsquo;</dt>
<dd><p>8x8 P-frame partition.
</p></dd>
<dt>&lsquo;<samp>p4x4</samp>&rsquo;</dt>
<dd><p>4x4 P-frame partition.
</p></dd>
<dt>&lsquo;<samp>b8x8</samp>&rsquo;</dt>
<dd><p>4x4 B-frame partition.
</p></dd>
<dt>&lsquo;<samp>i8x8</samp>&rsquo;</dt>
<dd><p>8x8 I-frame partition.
</p></dd>
<dt>&lsquo;<samp>i4x4</samp>&rsquo;</dt>
<dd><p>4x4 I-frame partition.
(Enabling &lsquo;<samp>p4x4</samp>&rsquo; requires &lsquo;<samp>p8x8</samp>&rsquo; to be enabled. Enabling
&lsquo;<samp>i8x8</samp>&rsquo; requires adaptive spatial transform (<samp>8x8dct</samp>
option) to be enabled.)
</p></dd>
<dt>&lsquo;<samp>none (<em>none</em>)</samp>&rsquo;</dt>
<dd><p>Do not consider any partitions.
</p></dd>
<dt>&lsquo;<samp>all (<em>all</em>)</samp>&rsquo;</dt>
<dd><p>Consider every partition.
</p></dd>
</dl>

</dd>
<dt><samp>direct-pred (<em>direct</em>)</samp></dt>
<dd><p>Set direct MV prediction mode. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>none (<em>none</em>)</samp>&rsquo;</dt>
<dd><p>Disable MV prediction.
</p></dd>
<dt>&lsquo;<samp>spatial (<em>spatial</em>)</samp>&rsquo;</dt>
<dd><p>Enable spatial predicting.
</p></dd>
<dt>&lsquo;<samp>temporal (<em>temporal</em>)</samp>&rsquo;</dt>
<dd><p>Enable temporal predicting.
</p></dd>
<dt>&lsquo;<samp>auto (<em>auto</em>)</samp>&rsquo;</dt>
<dd><p>Automatically decided.
</p></dd>
</dl>

</dd>
<dt><samp>slice-max-size (<em>slice-max-size</em>)</samp></dt>
<dd><p>Set the limit of the size of each slice in bytes. If not specified
but RTP payload size (<samp>ps</samp>) is specified, that is used.
</p>
</dd>
<dt><samp>stats (<em>stats</em>)</samp></dt>
<dd><p>Set the file name for multi-pass stats.
</p>
</dd>
<dt><samp>nal-hrd (<em>nal-hrd</em>)</samp></dt>
<dd><p>Set signal HRD information (requires <samp>vbv-bufsize</samp> to be set).
Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>none (<em>none</em>)</samp>&rsquo;</dt>
<dd><p>Disable HRD information signaling.
</p></dd>
<dt>&lsquo;<samp>vbr (<em>vbr</em>)</samp>&rsquo;</dt>
<dd><p>Variable bit rate.
</p></dd>
<dt>&lsquo;<samp>cbr (<em>cbr</em>)</samp>&rsquo;</dt>
<dd><p>Constant bit rate (not allowed in MP4 container).
</p></dd>
</dl>

</dd>
<dt><samp>x264opts (N.A.)</samp></dt>
<dd><p>Set any x264 option, see <code>x264 --fullhelp</code> for a list.
</p>
<p>Argument is a list of <var>key</var>=<var>value</var> couples separated by
&quot;:&quot;. In <var>filter</var> and <var>psy-rd</var> options that use &quot;:&quot; as a separator
themselves, use &quot;,&quot; instead. They accept it as well since long ago but this
is kept undocumented for some reason.
</p>
<p>For example to specify libx264 encoding options with <code>ffmpeg</code>:
</p><div class="example">
<pre class="example">ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
</pre></div>

</dd>
<dt><samp>a53cc <var>boolean</var></samp></dt>
<dd><p>Import closed captions (which must be ATSC compatible format) into output.
Only the mpeg2 and h264 decoders provide these. Default is 0 (off).
</p>
</dd>
<dt><samp>x264-params (N.A.)</samp></dt>
<dd><p>Override the x264 configuration using a :-separated list of key=value
parameters.
</p>
<p>This option is functionally the same as the <samp>x264opts</samp>, but is
duplicated for compatibility with the Libav fork.
</p>
<p>For example to specify libx264 encoding options with <code>ffmpeg</code>:
</p><div class="example">
<pre class="example">ffmpeg -i INPUT -c:v libx264 -x264-params level=30:bframes=0:weightp=0:\
cabac=0:ref=1:vbv-maxrate=768:vbv-bufsize=2000:analyse=all:me=umh:\
no-fast-pskip=1:subq=6:8x8dct=0:trellis=0 OUTPUT
</pre></div>
</dd>
</dl>

<p>Encoding ffpresets for common usages are provided so they can be used with the
general presets system (e.g. passing the <samp>pre</samp> option).
</p>
<a name="libx265"></a>
<h3 class="section">9.8 libx265<span class="pull-right"><a class="anchor hidden-xs" href="#libx265" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libx265" aria-hidden="true">TOC</a></span></h3>

<p>x265 H.265/HEVC encoder wrapper.
</p>
<p>This encoder requires the presence of the libx265 headers and library
during configuration. You need to explicitly configure the build with
<samp>--enable-libx265</samp>.
</p>
<a name="Options-25"></a>
<h4 class="subsection">9.8.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-25" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-25" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>preset</samp></dt>
<dd><p>Set the x265 preset.
</p>
</dd>
<dt><samp>tune</samp></dt>
<dd><p>Set the x265 tune parameter.
</p>
</dd>
<dt><samp>x265-params</samp></dt>
<dd><p>Set x265 options using a list of <var>key</var>=<var>value</var> couples separated
by &quot;:&quot;. See <code>x265 --help</code> for a list of options.
</p>
<p>For example to specify libx265 encoding options with <samp>-x265-params</samp>:
</p>
<div class="example">
<pre class="example">ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4
</pre></div>
</dd>
</dl>

<a name="libxvid"></a>
<h3 class="section">9.9 libxvid<span class="pull-right"><a class="anchor hidden-xs" href="#libxvid" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libxvid" aria-hidden="true">TOC</a></span></h3>

<p>Xvid MPEG-4 Part 2 encoder wrapper.
</p>
<p>This encoder requires the presence of the libxvidcore headers and library
during configuration. You need to explicitly configure the build with
<code>--enable-libxvid --enable-gpl</code>.
</p>
<p>The native <code>mpeg4</code> encoder supports the MPEG-4 Part 2 format, so
users can encode to this format without this library.
</p>
<a name="Options-26"></a>
<h4 class="subsection">9.9.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-26" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-26" aria-hidden="true">TOC</a></span></h4>

<p>The following options are supported by the libxvid wrapper. Some of
the following options are listed but are not documented, and
correspond to shared codec options. See <a href="#codec_002doptions">the Codec
Options chapter</a> for their documentation. The other shared options
which are not listed have no effect for the libxvid encoder.
</p>
<dl compact="compact">
<dt><samp>b</samp></dt>
<dt><samp>g</samp></dt>
<dt><samp>qmin</samp></dt>
<dt><samp>qmax</samp></dt>
<dt><samp>mpeg_quant</samp></dt>
<dt><samp>threads</samp></dt>
<dt><samp>bf</samp></dt>
<dt><samp>b_qfactor</samp></dt>
<dt><samp>b_qoffset</samp></dt>
<dt><samp>flags</samp></dt>
<dd><p>Set specific encoding flags. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>mv4</samp>&rsquo;</dt>
<dd><p>Use four motion vector by macroblock.
</p>
</dd>
<dt>&lsquo;<samp>aic</samp>&rsquo;</dt>
<dd><p>Enable high quality AC prediction.
</p>
</dd>
<dt>&lsquo;<samp>gray</samp>&rsquo;</dt>
<dd><p>Only encode grayscale.
</p>
</dd>
<dt>&lsquo;<samp>gmc</samp>&rsquo;</dt>
<dd><p>Enable the use of global motion compensation (GMC).
</p>
</dd>
<dt>&lsquo;<samp>qpel</samp>&rsquo;</dt>
<dd><p>Enable quarter-pixel motion compensation.
</p>
</dd>
<dt>&lsquo;<samp>cgop</samp>&rsquo;</dt>
<dd><p>Enable closed GOP.
</p>
</dd>
<dt>&lsquo;<samp>global_header</samp>&rsquo;</dt>
<dd><p>Place global headers in extradata instead of every keyframe.
</p>
</dd>
</dl>

</dd>
<dt><samp>trellis</samp></dt>
<dt><samp>me_method</samp></dt>
<dd><p>Set motion estimation method. Possible values in decreasing order of
speed and increasing order of quality:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>zero</samp>&rsquo;</dt>
<dd><p>Use no motion estimation (default).
</p>
</dd>
<dt>&lsquo;<samp>phods</samp>&rsquo;</dt>
<dt>&lsquo;<samp>x1</samp>&rsquo;</dt>
<dt>&lsquo;<samp>log</samp>&rsquo;</dt>
<dd><p>Enable advanced diamond zonal search for 16x16 blocks and half-pixel
refinement for 16x16 blocks. &lsquo;<samp>x1</samp>&rsquo; and &lsquo;<samp>log</samp>&rsquo; are aliases for
&lsquo;<samp>phods</samp>&rsquo;.
</p>
</dd>
<dt>&lsquo;<samp>epzs</samp>&rsquo;</dt>
<dd><p>Enable all of the things described above, plus advanced diamond zonal
search for 8x8 blocks, half-pixel refinement for 8x8 blocks, and motion
estimation on chroma planes.
</p>
</dd>
<dt>&lsquo;<samp>full</samp>&rsquo;</dt>
<dd><p>Enable all of the things described above, plus extended 16x16 and 8x8
blocks search.
</p></dd>
</dl>

</dd>
<dt><samp>mbd</samp></dt>
<dd><p>Set macroblock decision algorithm. Possible values in the increasing
order of quality:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>simple</samp>&rsquo;</dt>
<dd><p>Use macroblock comparing function algorithm (default).
</p>
</dd>
<dt>&lsquo;<samp>bits</samp>&rsquo;</dt>
<dd><p>Enable rate distortion-based half pixel and quarter pixel refinement for
16x16 blocks.
</p>
</dd>
<dt>&lsquo;<samp>rd</samp>&rsquo;</dt>
<dd><p>Enable all of the things described above, plus rate distortion-based
half pixel and quarter pixel refinement for 8x8 blocks, and rate
distortion-based search using square pattern.
</p></dd>
</dl>

</dd>
<dt><samp>lumi_aq</samp></dt>
<dd><p>Enable lumi masking adaptive quantization when set to 1. Default is 0
(disabled).
</p>
</dd>
<dt><samp>variance_aq</samp></dt>
<dd><p>Enable variance adaptive quantization when set to 1. Default is 0
(disabled).
</p>
<p>When combined with <samp>lumi_aq</samp>, the resulting quality will not
be better than any of the two specified individually. In other
words, the resulting quality will be the worse one of the two
effects.
</p>
</dd>
<dt><samp>ssim</samp></dt>
<dd><p>Set structural similarity (SSIM) displaying method. Possible values:
</p>
<dl compact="compact">
<dt>&lsquo;<samp>off</samp>&rsquo;</dt>
<dd><p>Disable displaying of SSIM information.
</p>
</dd>
<dt>&lsquo;<samp>avg</samp>&rsquo;</dt>
<dd><p>Output average SSIM at the end of encoding to stdout. The format of
showing the average SSIM is:
</p>
<div class="example">
<pre class="example">Average SSIM: %f
</pre></div>

<p>For users who are not familiar with C, %f means a float number, or
a decimal (e.g. 0.939232).
</p>
</dd>
<dt>&lsquo;<samp>frame</samp>&rsquo;</dt>
<dd><p>Output both per-frame SSIM data during encoding and average SSIM at
the end of encoding to stdout. The format of per-frame information
is:
</p>
<div class="example">
<pre class="example">       SSIM: avg: %1.3f min: %1.3f max: %1.3f
</pre></div>

<p>For users who are not familiar with C, %1.3f means a float number
rounded to 3 digits after the dot (e.g. 0.932).
</p>
</dd>
</dl>

</dd>
<dt><samp>ssim_acc</samp></dt>
<dd><p>Set SSIM accuracy. Valid options are integers within the range of
0-4, while 0 gives the most accurate result and 4 computes the
fastest.
</p>
</dd>
</dl>

<a name="mpeg2"></a>
<h3 class="section">9.10 mpeg2<span class="pull-right"><a class="anchor hidden-xs" href="#mpeg2" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-mpeg2" aria-hidden="true">TOC</a></span></h3>

<p>MPEG-2 video encoder.
</p>
<a name="Options-27"></a>
<h4 class="subsection">9.10.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-27" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-27" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>seq_disp_ext <var>integer</var></samp></dt>
<dd><p>Specifies if the encoder should write a sequence_display_extension to the
output.
</p><dl compact="compact">
<dt><samp>-1</samp></dt>
<dt><samp>auto</samp></dt>
<dd><p>Decide automatically to write it or not (this is the default) by checking if
the data to be written is different from the default or unspecified values.
</p></dd>
<dt><samp>0</samp></dt>
<dt><samp>never</samp></dt>
<dd><p>Never write it.
</p></dd>
<dt><samp>1</samp></dt>
<dt><samp>always</samp></dt>
<dd><p>Always write it.
</p></dd>
</dl>
</dd>
</dl>

<a name="png"></a>
<h3 class="section">9.11 png<span class="pull-right"><a class="anchor hidden-xs" href="#png" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-png" aria-hidden="true">TOC</a></span></h3>

<p>PNG image encoder.
</p>
<a name="Private-options-1"></a>
<h4 class="subsection">9.11.1 Private options<span class="pull-right"><a class="anchor hidden-xs" href="#Private-options-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Private-options-1" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>dpi <var>integer</var></samp></dt>
<dd><p>Set physical density of pixels, in dots per inch, unset by default
</p></dd>
<dt><samp>dpm <var>integer</var></samp></dt>
<dd><p>Set physical density of pixels, in dots per meter, unset by default
</p></dd>
</dl>

<a name="ProRes"></a>
<h3 class="section">9.12 ProRes<span class="pull-right"><a class="anchor hidden-xs" href="#ProRes" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-ProRes" aria-hidden="true">TOC</a></span></h3>

<p>Apple ProRes encoder.
</p>
<p>FFmpeg contains 2 ProRes encoders, the prores-aw and prores-ks encoder.
The used encoder can be chosen with the <code>-vcodec</code> option.
</p>
<a name="Private-Options-for-prores_002dks"></a>
<h4 class="subsection">9.12.1 Private Options for prores-ks<span class="pull-right"><a class="anchor hidden-xs" href="#Private-Options-for-prores_002dks" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Private-Options-for-prores_002dks" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>profile <var>integer</var></samp></dt>
<dd><p>Select the ProRes profile to encode
</p><dl compact="compact">
<dt>&lsquo;<samp>proxy</samp>&rsquo;</dt>
<dt>&lsquo;<samp>lt</samp>&rsquo;</dt>
<dt>&lsquo;<samp>standard</samp>&rsquo;</dt>
<dt>&lsquo;<samp>hq</samp>&rsquo;</dt>
<dt>&lsquo;<samp>4444</samp>&rsquo;</dt>
</dl>

</dd>
<dt><samp>quant_mat <var>integer</var></samp></dt>
<dd><p>Select quantization matrix.
</p><dl compact="compact">
<dt>&lsquo;<samp>auto</samp>&rsquo;</dt>
<dt>&lsquo;<samp>default</samp>&rsquo;</dt>
<dt>&lsquo;<samp>proxy</samp>&rsquo;</dt>
<dt>&lsquo;<samp>lt</samp>&rsquo;</dt>
<dt>&lsquo;<samp>standard</samp>&rsquo;</dt>
<dt>&lsquo;<samp>hq</samp>&rsquo;</dt>
</dl>
<p>If set to <var>auto</var>, the matrix matching the profile will be picked.
If not set, the matrix providing the highest quality, <var>default</var>, will be
picked.
</p>
</dd>
<dt><samp>bits_per_mb <var>integer</var></samp></dt>
<dd><p>How many bits to allot for coding one macroblock. Different profiles use
between 200 and 2400 bits per macroblock, the maximum is 8000.
</p>
</dd>
<dt><samp>mbs_per_slice <var>integer</var></samp></dt>
<dd><p>Number of macroblocks in each slice (1-8); the default value (8)
should be good in almost all situations.
</p>
</dd>
<dt><samp>vendor <var>string</var></samp></dt>
<dd><p>Override the 4-byte vendor ID.
A custom vendor ID like <var>apl0</var> would claim the stream was produced by
the Apple encoder.
</p>
</dd>
<dt><samp>alpha_bits <var>integer</var></samp></dt>
<dd><p>Specify number of bits for alpha component.
Possible values are <var>0</var>, <var>8</var> and <var>16</var>.
Use <var>0</var> to disable alpha plane coding.
</p>
</dd>
</dl>

<a name="Speed-considerations"></a>
<h4 class="subsection">9.12.2 Speed considerations<span class="pull-right"><a class="anchor hidden-xs" href="#Speed-considerations" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Speed-considerations" aria-hidden="true">TOC</a></span></h4>

<p>In the default mode of operation the encoder has to honor frame constraints
(i.e. not produce frames with size bigger than requested) while still making
output picture as good as possible.
A frame containing a lot of small details is harder to compress and the encoder
would spend more time searching for appropriate quantizers for each slice.
</p>
<p>Setting a higher <samp>bits_per_mb</samp> limit will improve the speed.
</p>
<p>For the fastest encoding speed set the <samp>qscale</samp> parameter (4 is the
recommended value) and do not set a size constraint.
</p>
<a name="libkvazaar"></a>
<h3 class="section">9.13 libkvazaar<span class="pull-right"><a class="anchor hidden-xs" href="#libkvazaar" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-libkvazaar" aria-hidden="true">TOC</a></span></h3>

<p>Kvazaar H.265/HEVC encoder.
</p>
<p>Requires the presence of the libkvazaar headers and library during
configuration. You need to explicitly configure the build with
<samp>--enable-libkvazaar</samp>.
</p>
<a name="Options-28"></a>
<h4 class="subsection">9.13.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-28" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-28" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>b</samp></dt>
<dd><p>Set target video bitrate in bit/s and enable rate control.
</p>
</dd>
<dt><samp>kvazaar-params</samp></dt>
<dd><p>Set kvazaar parameters as a list of <var>name</var>=<var>value</var> pairs separated
by commas (,). See kvazaar documentation for a list of options.
</p>
</dd>
</dl>


<a name="Subtitles-Encoders"></a>
<h2 class="chapter">10 Subtitles Encoders<span class="pull-right"><a class="anchor hidden-xs" href="#Subtitles-Encoders" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Subtitles-Encoders" aria-hidden="true">TOC</a></span></h2>

<a name="dvdsub-1"></a>
<h3 class="section">10.1 dvdsub<span class="pull-right"><a class="anchor hidden-xs" href="#dvdsub-1" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-dvdsub-1" aria-hidden="true">TOC</a></span></h3>

<p>This codec encodes the bitmap subtitle format that is used in DVDs.
Typically they are stored in VOBSUB file pairs (*.idx + *.sub),
and they can also be used in Matroska files.
</p>
<a name="Options-29"></a>
<h4 class="subsection">10.1.1 Options<span class="pull-right"><a class="anchor hidden-xs" href="#Options-29" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Options-29" aria-hidden="true">TOC</a></span></h4>

<dl compact="compact">
<dt><samp>even_rows_fix</samp></dt>
<dd><p>When set to 1, enable a work-around that makes the number of pixel rows
even in all subtitles.  This fixes a problem with some players that
cut off the bottom row if the number is odd.  The work-around just adds
a fully transparent row if needed.  The overhead is low, typically
one byte per subtitle on average.
</p>
<p>By default, this work-around is disabled.
</p></dd>
</dl>


<a name="See-Also"></a>
<h2 class="chapter">11 See Also<span class="pull-right"><a class="anchor hidden-xs" href="#See-Also" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-See-Also" aria-hidden="true">TOC</a></span></h2>

<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>, <a href="ffserver.html">ffserver</a>,
<a href="libavcodec.html">libavcodec</a>
</p>

<a name="Authors"></a>
<h2 class="chapter">12 Authors<span class="pull-right"><a class="anchor hidden-xs" href="#Authors" aria-hidden="true">#</a> <a class="anchor hidden-xs"href="#toc-Authors" aria-hidden="true">TOC</a></span></h2>

<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
<samp>MAINTAINERS</samp> in the source code tree.
</p>


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